Learning a skill isn't really simple. You need to have credentials and work experience to monetize a skill. Even if I was an expert at something it's most likely not monetizable if you have no credentials or work experience. It takes 5-8 years to actually develop all of that. You have to go to college and go through internships. Somebody who is older simply can't afford the time and finances to do all of that.
Even for example trades. You have to through 5 years of minimum wage just to make a normal salary. Which is great if you are young but it doesn't work when you are past 25-30.
Obviously for safety reasons it's not a bad thing to have it set up this way, but it also locks people out of things. If you are homeless you most likely are locked out of developing a skill that can eventually be monetized.
Libertarians will act like life is runescape where you can just go grinda bit and suddenly your skill level goes up. In reality there's a lot of requirements that are mostly set up for younger people to achieve.