The working adults (my dc) who still live at home contribute financially towards the household. Because they live here and use things in it, such as internet, electric, water, food etc. Its not about 'rent' its about making a contribution as an earning adult to the things you use and not having someone else fund you. My DC still have much more disposable income than me a month and are still able to save because they are not paying extortionate private rent on top of regular bills.
I don't see why they shouldn't contribute. I am trying to raise decent young adults who do not think it ok to sponge off anyone for things they use, including their parent. And in fact both of mine (both under 20) actually offered the contribution before I had brought it up with them, so I think I have done a pretty good job of achieving that. Mine are looking at ways to move out in the course of the next few years and be fully independent, which in todays climate is pretty expensive, but they do not want to live with their mother well into adulthood
I do have friends who do not charge their dc rent, and the majority of those do not have as much saved as mine do, and appear in no rush to live independantly.
I don't know if it has anything to do with the fact that most who don't charge 'rent' also do pretty much everything for their dc and they don't help out much apparently (which my friends moan about).
It does depend heavily on everyones individual circumstances and also depends on the DC and whether they want to save/move out. But it does seem that those dc not encouraged to contribute in any way, do tend to stay at home much longer.
I also know of 5 different men in their 30's and one in his 40's who still live at home and do not pay anything, even though they are on good salarys. Not surprisingly, they all have parents who do all their cooking/washing/cleaning still.
I think there needs to be a balance. OP mentioned her parents were financially well off and she was encouraged to put away a sum each month where she couldn't touch it and was fortunate in that respect that she was able to save by her parents allowing her to live rent free. I'm sure we'd all love to be able to help our dc like that. But she has the right attitude in the first place. OP was independent thinking and did things at home to help out. And actively wanted to move out and independant. There are definitely some (alot?) of young adults who are not like this, and if they are not, then perhaps charging them a contribute to their living may steer those ones in the direction a bit more that life is not full of handouts and helps those ones to grow up a bit.
I do not know when mine will move out, or when they can afford it, but I do know they are thankfully not of the mindset that their life is free and cushy at home that they want to stay forever!