Probably not down to the teachers but to administration. When I was a kid we had computers (PC's or Macs) in some classrooms, but the caveat is that they specifically blocked most websites so if it wasn't on an approved list you couldn't use it. At some point it seems like they gave up trying to stay ahead of kids circumventing the blocks and teachers aren't spending time outside of class playing IT. They already dedicate a lot of unpaid time to grading papers and other extracurricular activities.

I can at least agree that teachers should confiscate or prevent students from using them if they provide more of a distraction than a help.