I haven't seen the other thread, but that would seem a little out of order. But students are going to be immature, they are still growing up.
a) I wouldn't really care, but I didn't want to live in halls in my final year let alone later. Once you have a group of friends and are established the need for halls diminishes.
b)Kind of related to the above, its a different social group and age group. I don't hang around with my sisters friends they aren't at the same stage of social development as me. I have friends my own age I have far more in common with and make better company. If I could go out with people my own age or different, I'd pick my own.
c)Most 40 year olds guys would like to, but most are either looking for girls in a more normal age range 28-40 for a relationship, or are in relationships. I guess it linked to them seeming like they don't really belong in the social group.
I guess its a judgement on motivations. The social side of uni is supposed to be about gaining life experience and meeting new people. The view of the mature student is one who already has life experience and is looking for purely further education. Perhaps they also want to meet new people, but you'd expect them to have less common ground with someone 2 decades younger. I guess there is a perception of someone trying to relive their youth, so they take on the kind of awkward dad like figure.
We had a few mature students, but they did tend to stick to the stereotype of only appearing at lectures, working hard and the only social interaction being course related discussions.