Well actually there are 96 of them in practice, I think it's tracked in increments of 15 minutes since anything less is a bit meaningless.
Of course in reality it's continuous so there are infinite timezones, but the only practical thing we can change are hours so minutes don't get offset and make planning even more of a nightmare. If we used a more sensible base 10 time keeping one could probably do more.
> picture how annoying it would be if you crossed a timezone line on your way to your (or your child's) school
I'm pretty sure this happens in the US to people on a daily basis? It's the unfortunate reality of living on a rotating sphere that you really can't avoid if you cross country/state lines often.
> they try to be useful
I don't see how it's useful to keep west Spain 2 hours late to their actual sunrise time. It must be rather maddening.