Compare each scenario to the first to see the effect of the changed assumption. The value of starting early, contributing as much as possible and earning a good return is evident. The earlier you start the better. Still worth doing at any age. It is a great benefit if you can get it.
Some companies provide no match.
It is still worth doing. If you get higher returns the result is dramatic. Any contribution is better than none. There are some problems with 401k's in the country today. Really there are.