You're probably going to want to whitelist a domain here and there relative to the default blacklist. And the pi-hole has a few blacklists that aren't enabled by default, since they are much more strict.
So pi-hole-as-a-service doesn't make too much sense.
Ok thats a good argument. But the few pihole-users i know do not have a single whitelisted domain and likely will never have one. Also I could still whitelist most domains by adding the ip to my etc/hosts
I'm a long time pi-hole user and follow the subreddit and discourse regularly. You'll find many a pi-hole user with whitelists. The following are pretty common.
Unfortunately some of the more extreme blacklists can block legitimate error-reporting software among others that I commonly use for work. Same goes if you work in analytics you'll have to open up some just to access your dashboard.
So pi-hole-as-a-service doesn't make too much sense.