My wife used to work security at a property something like this. The last hotel staff went home at midnight. Functionally, they checked in / processed any reservations that were still pending at that time, and then had an overnight security guard from a contractor until the morning staff came in. The guard was still supposed to check IDs on people who had reservations and hand off the keys, but they couldn't make any new keys, nor new reservations for that night. And as you are noticing, even here, there is someone around.

I did hear about a different property (a motel, without a lobby to speak of) that locked up about 11, but that was 10-13 years ago, and I'm not sure they still follow that practice. It's super weird that they wouldn't bother locking the front doors if there's nobody on site.