Google Play Services implements a lot of increasingly vital features and interfaces on Android. Not having it kills a good number of things people consider important, like push notifications (some apps are designed to still send push notifications like Signal, but it's kind of a hack and does drain the battery). If you're looking for almost the same functionality without google play services, MicroG[1] is an open source implementation of Google Play Services and its' associated components. I don't think it works on GrapheneOS unfortunately, but GrapheneOS already sandboxes all the Google Play Services components, so you should be fine as is. "Normal"/stock Android roms aren't set up the same way however, so you pretty much need either Google Play Services or MicroG for push notifications, location services, etc.

[1] - https://microg.org/

I do but ordinarily for services that are not anonymous in the first place. Banking, ride-sharing, so on.