Your company sent you to some shit hotels then. I think the earliest breakfast end time I've been to is 8am, and that one was a bit more expensive than the others. Most hotels I stay at serve breakfast until 10am.
I'm not the person you are replying to, but my experience has been that they don't make any new food after ~8AM and most of the good stuff is pilfered before then, so although they serve until 9 or 10, there's rarely anything left if you arrive close to the end (or anything that you'd want to eat)
Was it a Super8 or Motel 6? I bet it was. No place that offers breakfast and is also worth staying at at any price does that. On the bright side you now know where not to go.
When I traveled for work, we mostly used Mariott or Hyatt or occasionally Holiday Inn. Not much choice when you have to stay wherever the company has an account. The one I described above was Mariott.
Depending on the assignment, I often had to work nights, so "just get up earlier" wasn't really an option.
10 is late for most of them - 9 is pretty common. If you're at the kind of vacation place where you're hanging out and relaxing, maybe staying up late, waking up at 8 so you can get ready and get down to eat breakfast, doesn't feel like last relaxing, which is OP's point. Of course people can do it, but a lot of times we want to sleep in on vacation.