Security, including privacy, is about layers of hardening. In this case, minimization of leakage and other privacy concerns for some can still be worth the tradeoffs. For example, some apps literally refuse to work on a completely de-googled phone. (I ran one for many years with no google services). Also, the general control the user gets offers a lot more ability to harden than most android. I bricked my phone and am currently borrowing one and using stock android and there are things like facebook that are literally uninstallable... At least on lineage/graphene the user can actually control the system.