yeah think you’re right, but built on and interacting with are both fine. but, if i was building an app i’d consider it essential to be community minded - build out good relays to take the weight of my app, but also serve the community in return for the community of relays providing some redundancy for me. also, some sats mechanism per event relayed would incentivise operators.
Discussion
True tho you can't rely on the goodness of man at scale, unfortunately. The free rider issue will become apparent without costs attached. Paid interactions will solve for a lot of that but that also presents some issues as well in terms of whether people want to bear that cost (not financially, but psychologically)