@Linkat,
Some people may foolishly think they are but if you work for a company that matches even a percentage of your contributions they are the best investment anyone can make.
401Ks are low-risk investments and so the company match is an additional, incredibly high yield you can't get anywhere else.
Let's say you have a plan where your company only matches 50% and at the end of the year your account has made nothing in terms of investment yields...guess what? You made 50%! Where else can you get that yield?
Sure the market could utterly collapse and all of those contributions could be lost as well, but that hasn't happened and won't. Even in the Great Recession, company contributions offset personal contribution losses.
And I haven't even discussed the tax benefits
Any young person who has the opportunity to invest in a 401K and doesn't is making a big mistake, and if they don't because they think it's a scam, they are a fool and deserve to retire without money.
One of the best things the government ever did for the Average Joe!