If you work for a company that has a 401k then you need to sign up for it. If the company has a match percentage then that is the absolute minimum you should contribute. And when you are younger you should set it up as a Roth so you pay taxes on it now.
This isn't a thing you should do at a certain age. The younger you start the better. The money just comes out of your paycheck, same as taxes.
No. It's the exact opposite. It's your company not putting in the minimum to support it's employees.