A few stories:
I've had a student install a super cheap (g only) repeater to provide wifi to their car in the car park, due to its location a number of students ended up using that rather than our APs. This slowed access for them dramatically.
I've had a student physically remove an AP to get to the 2.5 gigabit port they connect to, they somehow thought that would be better than the 1G they have in their rooms, despite it all being the same link out.
An overseas student cloned a MAC of their device to a travel router and effectively ran a VPN server for their family to try and give them an IP in our country.
The accommodation only has an hour of my time per week or so, they're not paying a lot so issues only get dealt with when I have the time for them, this leads to an extended period of bad access for folks and my complaints to the staff.
The main point of the story is that not all students take the experience of their neighbors into account. Hence the restrictions.
Yea that is true, there's definitely either a profit motive or they don't think they have the bandwidth for everyone to have multiple devices and are this introducing an up charge/scarcity to cover up that.
The site I look after we have a restriction on device numbers, 5 per room. Even that is flexible and not really enforced as in reality the network will be fine with thousands even. The main restrictions are about device behavior and preventing causing interference or outages.
There's only 120 rooms in the site I look after so it's not massive.
We're running W-Fi 6 with all channels enabled including DFS channels. We've great coverage (roughly one access point per 4 -6 rooms in a 90s building).