angels already need quite a lot from you done, but if you're just a solo hacker and over the weekend build something useful and want to see if and who would pay for it - then angels are not even looking at you. Think like equity crowdfunding, but with lots of gamified initiatives, like mixing crowdfunding sites with investing characteristics. Makes sense?
The biggest road block IMO is that there are tons of people with "the next great Unicorn app idea", overwhelming numbers who's ideas are well beyond their means to implement or just plain bad to begin with. Having just a little road bump of needing to actually make something first filters out a lot of people.
As far as making money before you've done anything to prove out your idea and your ability to make it though it's pretty spot on.
The reason there's not many people interested is people with ideas are a dime a dozen, the people able to implement it given the resources are a thin slice of that group.