Around my area, it is usual for therapists to have night or saturday or even sunday appointments. I agree people in private practice get to choose their own hours.
I personally care nothing about families and would not choose to pay a therapist who told me their hours were 9-5 because of their children. If the therapist was all family focused - they would not be the therapist for me to hire.
I like setting my own hours too - and they are not 9-5. I like that I have flexibility and can set whatever hours work for me.
The first therapist I ever saw worked from 9-5 a couple of days a week and then 12- 8 other days and on Saturday afternoon. She had children at home. She took off Sundays and Tuesdays.

Also - the dentist I see does not just have 9-5 hours - she has a late night and saturday appointments. I think she does not work on Mondays. The gp of my partner works on Saturdays. Other professionals sometimes do keep hours that are in place to help people.