I think bosses like meetings because they're not as interested, sometimes, in people following the edicts as they are in people doing as _they_ say. It's important for them to be the one telling you and you having to obey. If you just did what an email says then that's just working for the business; the machine is working. If you attend a meeting then, it appears at least, the boss is the one who controls you rather than your actions being directed to the business needs you're [apparently] working for the boss. They say jump, you say how high.

Maybe it's minor megalomania. IME that's another reason for meetings.