Investing in startups is hard, as I am sure Y-Combinator would attest. The layperson is not prepared to invest in them. To vet the companies, their leadership, the feasibility of their ideas, etc... Especially with a low payout. I can understand the SEC's hesitation as this could easily lead to scams. Just look at kickstarter and all the things that have gone down there.

Really what the parent is proposing is something like -

Here is a savings account. You can throw chunks of money in it at startups that have a high chance of failing. But if they succeed you'll only earn bank level interest since it's not capital investment. So you have a small chance at earning bank level interest.

Where is the incentive?