I've wondered about that. Take your PO to the bank, and they'll be more than accommodating in setting you up with a revolving line of credit. Why give up equity? Sometimes they do say "go away, you don't need me", but other times they snap the company up.
A lot of people are pretty explicit that they are looking to leverage the sharks specifically. The sharks are also pretty explicit, frequently saying "this is a good idea but not good enough for the amount of work I'd have to put in".
You can tell the ideas that the sharks think are good because they talk about how much of their time they're willing to give, not just the money.
