my implication was more of a...people not trusting that he has the money because of his age or thinking that at 20 he'll be a horrible investor who doesn't know what he is getting into.
And yes most people only want the money, but money comes from different sources. Would you really want a crack dealer as your investor? How about someone with a criminal record?
Yaw, certainly most of us have the luxury (or wisdom, at least!) of saying no to destructive/unscrupulous investors.
And yeah, I think most 20 year old folks would be terrible at investing (I'm pretty sure I would've been at 20-- hell, maybe now!). We have a 24 year old investor, FWIW.
But I think there is this (largely incorrect) notion that your investors are going to be working for you. For the most part, they aren't. Oh, they'll keep their eyes peeled for opportunities for you. And if you are on fire, they might smell the win and start pouring on some effort. But for the most part, they are filthy rich, have tons of investments, and tons of interests. They are stretched SUPER thin and their time is way more scarce than their money.
My favorite quote from a YC dinner (names redacted):
Q: "How to you make sure you get investors who bring more than money to the table?"
A: Famous Internet Entrepreneur: "What? Investors don't bring anything to the table other than money. Wait. Scratch that. One time [famous web 2.0 investor] carried a few servers up a flight of stairs for us."
(that's paraphrased, but that exchange actually happened)
And yes most people only want the money, but money comes from different sources. Would you really want a crack dealer as your investor? How about someone with a criminal record?