I don’t know. Well, I’m also not a student anymore in the classic sense, but I regularly do some kind of “continuous education” with various institutes, so I get some .ac.uk addresses. Some services allow you to use 1 address only 1 time for 1 year to get a cheaper subscription. But I studied with various institutes, so various different addresses and one time I was even lucky and a University changed their emails to another subdomain because they switched from G Suite to M365, so I could use the new email again to get a cheaper 1 year subscription. So I got cheaper music subscriptions for many years, 1 year free YNAB, and probably other services which I can’t remember right now. I also haven’t paid for an M365 subscription for years
Some people forget they can also use that email address to get cheaper subscriptions even though they are not an undergrad full-time student anymore but also when they work full-time and just do some postgrad studies / MBA / coursework / certificate or whatever on the side.