I worked in a University for decades, and still do on an occasional basis, and can honestly say that the drinking culture was far worse in my own student days than it is now. There is a greater tolerance of those with cultural reasons not to drink, and a corresponding rise in the number of events held on non-licensed premises. There is also a rise in the number of health-conscious young people who are more likely to go to the gym after lectures than to the SU bar.
Nevertheless, of course there will be exuberance and parties, and all the things that young people will want to do - it's nature's way. Selfish? I don't know.
The measures being taken on campuses regarding social distancing, cleaning etc will make the University buildings as safe as workplaces, so that leaves Halls of Residence and privately rented accommodation. My guess is that in the Halls there will be rules about distancing - there were rules over the summer about keeping to one person at a time in the kitchen and so on - and in rented flats it will be up to the students themselves to regulate. I have no reason to think that they will do so any less scrupulously than others of their age - why would they?
They are learning to become adults without parental guidance, and yes, they will make mistakes, but on the whole, young people are no less responsible than older ones. Please let's stop stereotyping one another?