Not everybody hacks on everything. Many of us pick and choose our hobbies. I don't sysadmin my phone for the same reason.
Why? Specialization is a thing. Not everyone specializes in security. Which let's be real, being an expert in security is really difficult, especially since it's a constantly moving goal post. Unless you're an expert it's probably not a good idea to roll your own.
Also, to run your own service you must specialize in security AND devops. The two thing overlaps a bit, but not 100%. And you must hope that every contact you are talking to has the same knowledge.
so much this - you can make a service 100% secure - by shutting it down. But if you want to stay online and be secure at the same time, there's always some resource tradeoff between the two
If you know a problem is hard and the consequences for doing it wrong are potentially serious, it would be irrational to not consider selecting a well-managed third party solution. Being a hacker doesn't mean being all-knowing and the best hacks are done with the knowledge of human limits (both of the hacker and of the maker of the system being hacked).