Diversity, my friend. What will you do if the 401k doesn’t come through like you want? Bear in mind that the ultra rich and the big banks employ people who are really good at investing money. They have more experience and information than you. They’ll bail themselves, but not you, out in case of disaster.
“Show me the money” is not a good motto for long term savings. Inflation or poor investment can make that money disappear easily enough. Of course you don’t want to get scammed, so oversight is a good idea.