It's simple, I don't have things like that that I need to do on any sort of daily basis.

I have a work calendar for work meetings, but never saw a need for personal calendar.

OK sure I put doctor and dentist on my personal calendar, but dentist is 2x a year and doctor is like once a year for a physical. On my personal calendar I might have a dozen things put on it for the whole year. Some upcoming family event, some wedding, etc.