Where I live, buses have a few points where they 'synchronize'. That means they wait there long enough to be exactly on schedule.
This to prevent people missing a bus that goes every hour because it was 5 minutes early.
The "El" (Elevated) trains in Chicago will do the same thing. Sometimes you simply stop between stations. Sometimes, it is only 25 ft before a station and you can see your goal in sight.
Why would they stop for regulation (as opposed to the track in front being occupied, which is obviously a good reason to stop at any place) at anything else but a station?
It's annoying when you’re on that bus, but it makes sense to try and avoid services bunching together.
(And occasionally when they do end up bunched together, the overcrowded bus in front will wait briefly so the empty bus behind it can pass)