They probably do that when one plays all the way through because people let shit continue to play without being there, and they can count that as an impression and get paid for it if they just inject a bunch of them to an active but unmonitored stream. The fact that you actually sat through it is completely irrelevant to them. Most people would have closed it out or went back in the video to whenever they left, which would likely reset the ad serving instruction.

Speculation, of course, but the sort of fuckery every big company is doing these days.

Also, creators don’t really get money from ads. Don’t feel bad for skipping them. Sponsorships and direct donations are basically the only ways creators make anything worth making on YouTube. Many creators will tell you as much themselves.