This just is not correct. For one, both my vangaurd and td ameritrade etf's outperform my work-driven handcock 401k. They match up to 10k, so i contribute and get their free money, but it wouldn't make sense for me to dump everything I own into it after that when that same money can work harder elsewhere.
Also, diversification is a real thing. You wouldn't put all of your money into a single stock, and you shouldn't keep all of your money in a single location. That way, if something happens - say the index that your 401k plays in gets Enron'd and completely ****s the bed, you haven't lost all your money. Diversify, diversify, diversify.
I funded my td ameritrade account with 10k and set it to high-risk. I could afford to take that hit if things **** the bed. I just bought it after the awful month of august so i'm hopeful things can turn around. My vanguard account is much more nested and low-risk. I use Robinhood like an autist to get my gambling out and try to swing for the fences. I usually keep it 2k and under because that **** is dangerous.
Imagine just lumping all your cash into one ****ing place, LMAO.