Except the few places without public transportation, most parents don't have to take their kids to school. Starting later would probably help with overprotective parents.
Are school buses not a thing anymore? The suburb I grew up in definitely didn't have a remotely decent public transit system but the school district was required (along with all public school districts in the state of Texas IIRC) to provide a school bus that stopped within a few minutes' walk of every student's home (probably with exceptions for people who actually lived outside of the school boundaries and applied to transfer in). In high school, classes started after 9am and it all seemed to work just fine.
No, they aren't really in many places. Our district runs a couple routes with limited stops, but nothing like I remember growing up 40 years ago.
You don’t always have to bring them there, but young kids do need help with getting ready for school.
Depending on where you live, it's probably not safe (and maybe even forbidden) to let young children (<10 years) go to and on public transportation alone.