A recent LTT video attributes it to hotels colluding so that one's Wi-Fi isn't too much better than the others.
Convention wireless is a pain in the ass as a whole, and I've seen it both from venue-hosted networks and privately-operated-on-site networks being deployed as an overlay.
It might or might not be connected to the show floor issues, but it's relevant information for a bunch of the in-room internet experience to get significantly worse over time. It suggests that they are not even trying, so the fact that convention wireless is hard is not an excuse.