I think when you're in your early 20s, you actually need to buy moe clothes than older people, as you don't always have a suitable wardrobe for work, and when you're invited to an event you are less likely to have something suitable to wear in the back of the wardrobe. It's hard, when, say, you've just finished uni, to go out and buy all the clothes you need for work at once- so people might buy a couple of items every month to spread the cost and build up their wardrobe.
I don't actually know anyone who goes to the beautician that regularly, mostly only for a special occasion, or as a treat they've saved up for.
I do know a lot of people who change their phone when their phone contract ends, and things like that, but not doing so would probably only save them a small amount a month by switching to a sim only contract. Not enough to pay for a deposit on a house, or even a car.
Most people in their 20s I know do own their own cars, that they've saved up to pay for. They can manage to save something like £2-5k as that's a more realistic goal than the £20-40k you need to buy a house. Also, it's scary to commit to a morgage if you don't have that much job stability. It's also much easier to move from rented accomadation if you need to move for work.
Tbh, I don't think older people have the right to judge young people's spending habits or financial choices. It's not people under 30 who've messed up the economy, it's older people. We're just the ones who will have to clean up the mess, and probably work until we're 70 and not get a pension.