I’d love to dabble with something like Graphene OS, but I find the Google Dialer Spam Call/Text Protection and Hold For Me features indispensable. Right now as far as I’m aware, those don’t work with Graphene. Also, I’m on the Advanced Protection program with Google so it is a no go for me as far as I’m aware.
They’re separate because Waze has a reputation of giving more “aggressive” routing, and has a social aspect to it. Stuff that really doesn’t belong in Google Maps.