The subject of social class in tabletop roleplaying games (RPGs) is a delicate, if understated one—delicate because it’s a real-world issue that’s still relevant in modern society; and understated, paradoxically, because everybody has an opinion on it and said opinion is often a vehement one. A lot of classic RPG adventuring involves treating the laws and customs of civilized society as merely being quaint rules that apply to other people; often players don’t want to hear about how there are complex conditions in place that limit how one’s character interacts with the upper classes. Particularly if their player-characters (PCs) are not part of the upper classes themselves*.
So if a gamemaster (GM) and his players just want to ignore class, by all means, go ahead. People ignore personally unpleasant facets of history in their personal RPG campaigns all the time, and that’s perfectly legitimate. But if the gaming group wants to explore some of this stuff, well, there can be stories in it. But there’s some things that have to be considered.
First off, contrary to popular belief and bad fiction, there typically are a lot of gradations in class (as well as caste, which can shade into the concept of class, and vice versa). Low/Middle/High classes only look uniform from the outside; on the inside they’re usually a patchwork of common assumptions, unspoken rules, and equally unspoken restrictions. And class restrictions are generally largely enforced from the inside, often by the very people most restricted by those restrictions—whether or not it’s logical to do so. Or at least logical from an outsider’s perspective: from the inside, the vision of a society that’s orderly enough to produce food without too many bandit raids can be curiously seductive.
Related to this last thought is the second one: it is likewise bad fiction to simply say something like “the aristocrat will ignore the peasant’s warning.” There’s always a communications channel between classes. The feudal baron will listen to the Chief Huntsman about strange howls in the wood, or to the housekeeper about guests skulking about after dark. If the Sergeant-Major saw something in the night, and the green subaltern did not, the regimental commander will double the guard. Any culture that wants to survive in the long term will come up with ways to allow the people running things to get something approaching accurate reporting from the people at the bottom of the social pyramid.
One last thing to remember is: just because a particular society is unfair and doesn’t allow people to live up to their potential, doesn’t mean that the society in question doesn’t work. The guy who wrote The Peter Principle (that’s the guy who came up with the entire ‘rise to the level of your incompetence’ thing) noted in his book that the British colonial system, by its nature, could and did prevent capable people of the ‘wrong’ class from rising to their level of incompetence. As a result, many of the day-to-day bureaucratic positions were held by people who could do the job and who weren’t going to get promoted out of that job. Which was all to the benefit of the British colonial system.
Now, whether you think that’s good social science or not—it’s quite possibly not—you can still use it to good effect in a game. In fact, you can use class systems to handily justify adding an unexpected complication or benefit to an adventure, for the sake of pacing. Is the party moving too quickly through the plot? Add an adversarial non-player character (NPC) who would normally be considered too competent to have his position, or is simply highly motivated to protect the class system that gives him a position of authority and power over people of his class. Want to speed things up? Give the party access to somebody who has the ear of the people who run the society, even if it’s just a case of let’s-hear-him-out. Or perhaps you only want to get the party focused? Take away one of their victories because somebody else knows how to better play the class relationships game. That’s always good for getting gamers’ attention.
Just keep in mind that class is a touchy issue in the real world. Particularly in, say, the United States, where one’s opinion of the very concept of ‘class consciousness’ as a real thing** says many significant things about one’s political opinions…
*As Lois McMaster Bujold once noted, egalitarians can function quite well in an aristocracy, just as long as they get to be aristocrats.
**Well, real thing for Americans. Most of us will readily admit that foreigners have it.