If you use someone else's relay you don't need to expose your IP address to your users.
Discussion
Yeah, it's a minor privacy improvement, however I don't think many will run DVMs without running relays as well.
(btw, I've just sent you a DM, so I announce it here give how reliable they are 😅 )
Imagine a DVM running on an ESP-32 pointed at the damus relay. It's a globally accessible API you can plug in anywhere with WiFi coverage.