I’ve been having this issue as well, here is my guess as to the explanation.
When you disconnect from a server you get priority on logging back into it if you were in the middle of something. This might explain why players seem to be cutting in front of you in line.
Additionally, there appears to be a small “grace period” if you’re in queue and you leave and come back. If you rejoin the queue within a short window of time, you can reclaim your previous spot.
For example, I’m waiting in a huge queue for a High-pop server right now, but I just left queue quickly to check what the wait time was on the other server I play on. I decided to rejoin the first queue and when I did that I was at first put at the back of the line (~20,000 players ahead of me), then after a second or two the queue updated and I was placed back at my position in the queue where I had been a few seconds before (~10,000 ahead of me.)
I think these two things combined explain why players seem to be cutting in front of you in queues, players who disconnect or leave and rejoin the queue within a short window of time have a grace period to get back in line rather than having to go right to the back.