My daughter had preschool, from 3-4 years old. Then when she was almost 5, she went to Kindergarten.
My son, started at about 4.5 years old.
They both LOVE LOVE LOVE it.
Prior to that, I home schooled them.
I enrolled them in Preschool, because it is beneficial to them. They attend Preschools that suited THEM and that THEY liked. As well as myself. I scouted Preschools, with them.
My son for example, does not go to the same preschool, that my daughter did.
Both my kids, have told me, pointedly, that they loved/love their Preschool. They learn many things there. Aside from what I taught them.
It also prepared them for Kindergarten. The bigger social/emotional things about it and being in groups with a 'Teacher.' It is not just 'academic' reasons. It is the whole child and what they get out of it.
It is also about being 'away' from Mommy. And growing in that respect as well and maturing.
My son only goes part-time. But he has told me he wishes he can go everyday. But we can't afford it.
My daughter started out part-time. Then per her telling us, she wanted to go everyday. So we did. At that time, we could afford everyday for her.