Touched on in the crossover episodes of The Flash (2014) and Arrow; The Flash's superspeed would make cleaning up a lot of Starling City's issues easier, but Barry doesn't have the tactical awareness that Ollie does; the latter fights the former to a draw with no powers and sticks him with an ambush arrow on two occasions when Barry thinks he's got the upper hand. Star City's villains are usually more violent. Barry disagrees with Oliver's more gray-zone morality when it comes to fighting Starling's darker criminals. "Flash vs. Arrow" makes clear that the CCPD find the Arrow an unwelcome presence due to his vigilante killings in season 1, and Oliver has real trouble facing people with superpowers (not to mention a pissed-off gorilla with Psychic Powers). That said, when Barry has his Big Damn Heroes moment in Season 3 finale, the entire League of Assassins is shown to be hopelessly outclassed by a single speedster, especially since they have no idea he's coming. The trope is averted in major crossovers, such as the "Invasion!" arc, when it's "all hands on deck" in order to stop an Alien Invasion, requiring Team Arrow, Team Flash, the Legends, and Supergirl to work together.
Although averted a few times in Arrow when Oliver calls on Barry to make a quick stop over to do something for him then immediately leave, like help him and Diggle intercept a criminal before they leave the city, since Barry can be there and back in an instant without really taking much time out of his own problems (and since all it requires is a "Flash" streak shown running by without an appearance by Grant Gustin). Also averted in Flash's season 1 climactic battle against Reverse Flash where Barry does call for backup because he just can't take him alone. However besides Oliver only Firestorm shows up because Atom and Black Canary were unable thanks to events on their own show, and as this was early in the series run (where he'd yet to meet Supergirl and the Legends hadn't formed yet) no other heroes had started operating yet.
Stretched to unbelievability in the Arrow finale. Oliver's team is falling apart and mundane thugs are taking over the town, and he's willing to bring in some really questionable allies, but doesn't even try to call Barry. Possibly justified since the Thinker has sufficient power to stop them on his own.
However, in general played straight - Vixen, Flash, and Supergirl all stay in their own areas, despite being just a phone call away from each other.
In season 7 of Arrow, It's revealed that Roy Harper died and was resurrected by the Lazarus pit, which gives you a blood lust. Smart solution? Call Oliver, and have him call the Legends to get Constantine to purify Roy the same way he did Sara. Practiced solution? Try to keep the blood lust under control with drugs, and tell no one else, resulting in the deaths of two innocent guards.
Also happens in season 8, after William, Mia, and Connor somehow time-travel to 2019, no one thinks to call Team Flash or the Legends for their thoughts on time travel.
Exaggerated in the post-Crisis Black Lightning (2018), which now takes place in the same universe as the other Arrowverse shows. The country is under attack by a foreign power with an army of metahumans. Does Black Lightning think to call on the other heroes? No, of course not. He'd much rather use children to fight the Gravedigger and his army. For that matter, Gravedigger seems awfully focused on Freeland, even though Central City arguably has more metas than Freeland. In the final season there is exactly one occasion when Jefferson calls his friends at S.T.A.R. Labs for help ... with the science. The gadget is apparently delivered at superspeed, but Barry doesn't stick around.
This is addressed as Kara's desire to strike out on her own as a superhero in the world, so she defends National City while Clark stays in Metropolis. When James Olsen has to call Superman to save Supergirl from dying to an attack from Reactron, Kara and James have an argument about whether or not he should have called Superman at all. At the end of the episode even James admits that he moved to National City to become his own man and not remain "Jimmy" forever. In that episode, Supergirl also notes a practical reason: villains will start to think she's an easy target and plague National City if she needs Superman to help her on every problem. Superman finally makes an appearance, when both Kryptonians have to stop a falling space shuttle. Clark then stays in National City for a few days, but it's revealed that he refuses to work with DEO because they keep kryptonite in storage. Near the end of Season 2, everyone wonders where Superman is, considering that Earth is the middle of an Alien Invasion. Clark did show up, but he was mind-controlled by Queen Rhea of Daxam into fighting Kara, resulting in Kara proving herself to be his equal or better. Clark then comes up with a way for Kara to beat Rhea with a Combat by Champion.
Although Superman has arrived to help save the day on occasion, his absence during the world-threatening Reign arc of Season 3 is puzzling, given the arc has several episodes in which is presence would not only have saved his cousin from a lot of pain and injury, but would have been a no-brainer, in particular when Supergirl is rendered comatose after a fight with Reign, technically leaving no one in National City with the same level of power - the fact Superman isn't called in borders on the irresponsible. Later, it's mentioned that he's working on the other side of the world, but you'd think he could pop in at Super-Speed. Similarly, given Supergirl has a device capable of transporting between worlds, someone should at least suggest asking The Flash, Steel or any of the other super-powered beings from the other universe to return Kara's favor for helping save their Earth several times. This is ultimately settled in Elseworlds (2018), as Clark decides to retire as Superman to marry Lois and prepare for a child on the way.
In the Elseworlds (2018) crossover, Batwomanreally doesn't want Oliver or Barry in Gotham, especially the Green Arrow (there are already enough vigilantes in Gotham). She doesn't mind Kara, though.
While Superman & Lois is just starting, so far there haven't really been any mentions of the other heroes. Even Clark hasn't mentioned his cousin once, even when a mysterious villain in Power Armor is attacking nuclear power plants all over the country, or when a bridge is collapsing in China. Why was Superman the only one to respond to that one? Supergirl is at least as strong as him.
Justified as the Season Two finale establishes that Superman & Lois takes place in a new reality from the 'prime' Arrowverse Earth, rather than taking place in the same universe as initially believed.
