Yes, you say you've started out small, with manual phone usage, etc. But then you go on to say: "So in the interest of ethics and fairness, I want to talk to restaurants about working with them directly on a better reservation system." Sounds like you want to scale it, and make money off of it yourself, after all.
Whereas it seems to me that for high-demand restaurants the manual approach, exists that way because it won't scale. Anyone can get a reservation, if they're willing to wait a few weeks, it doesn't matter what they're willing/able to pay. And once you automate that, how do you keep it from being abused and effectively turning into a sort of demand tax? In which case the restaurant could be pocketing that money themselves by simply making the cost of dining there that high in the first place, but if they didn't, it's probably because they didn't want to restrict so heavily based on spending ability. (Well, and because pricing/markets is tricky, and who knows if it would've been successful initially at a higher price... this part is just speculation on my end.)