To a certain extent, the reputation of rapiers being high class is Truth in Television. During The Renaissance and The Cavalier Years in Europe, rapiers were strongly associated with the style trends, behaviors, and values of the court and high society. They were worn with one's best clothing as a statement that one was both in touch with the latest fashion and prepared to defend their life and personal honor at all times. The fencing style taught for the rapier was also highly elegant and difficult to master, so that anyone wearing one was invoking Possession Implies Mastery and showing off their level of education and practice. On the other hand, someone wearing a rapier could have just as easily have bought it as a status symbol or attempt at social climbing without actually possessing the combat skills or good upbringing that were assumed to go with it. At Versailles where swords were part of the dress code you could actually rent them, and by the 18th century the rapier's replacement, the smallsword, was practically mandatory to wear whether or not you knew how to use it. Some were created more as a form of male jewelry than actual fighting weapons, with impractical materials such as pure silver or solid gold set with gemstones making up the hilt. Every age, of course, has ceremonial weapons, which should not be judged by the same standards as their fighting counterparts. Many Real Life monarchs loved rapiers and owned collections of all kinds, which exist in the world's museum collections today and are documented by inventories and portraits. While not an exclusively aristocratic weapon, it has always carried a certain association with Blue Blood.
Because of the novelty of the rapier, there were many traditionalists and Moral Guardians throughout Europe who questioned its military usefulness and blamed it for the decay of society, especially in England where fads introduced from Catholic Italy were treated with suspicion. The conservative fencing master George Silver and the experienced soldier Sir John Smythe argued that the rapier was causing young gentlemen to kill each other in senseless duels but was useless for serving one's country in warfare. They claimed that there was no space in the tight press of battle to draw those extremely long dueling rapiers from their scabbards or wield them effectively, that the thrust-oriented style of fencing threw away sound principles of defense, and that the narrow, hard-tempered blades would break upon encountering any sort of armor. Others complained about the covering of hilts with useless decoration, associating it with the spread of fashion puffed up with pride, and contrasting their time with an imagined golden past when people were more modest.
While it is true that the rapier has certain drawbacks, modern consensus is that these anti-rapier diatribes were considerably overblown. A pervasive culture of constant weapon wearing and willingness to kill over the littlest slight was more to blame for the scourge of dueling than how long or broad the swords were. Lots of stereotypes about the rapier just aren't true, or don't acknowledge how much they really varied. It's common for it to be written about as if it were a weightless, flimsy weapon like a modern fencing epee, or else a ponderous and bulky predecessor to the lighter and quicker weapons classical fencing. By and large, rapiers were effective swords when used by capable hands. Their real strength was unarmored dueling and self defense, but they still had enough sturdiness to defend decently against even heavy weapons in a pinch. And that's just the archetypal dueling rapier we're talking about. There were also so-called "sword-rapiers" or "cavalry rapiers" that were really just the old-fashioned knightly sword with a fancy hilt, and the use of the term "side sword" to describe any rapier-like weapon with a broad blade is just another imperfect modern attempt to classify a chaotic situation. Some sword buffs simply throw up their hands after being frustrated trying to pin down a satisfactory definition of what is or isn't a rapier, and make do with "I know it when I see it".
