I continue to think that it's no coincidence that it tends to be women who say this. I am not yet convinced of the existence of the straight male platonic friend (I mean, from the male's private point of view).
Perhaps that is because I have noticed that women are more likely to think in shades of grey and men are either/or.
I normally hate making blanket statements but physically female brains have more connections between the halves so perhaps this is the reason?
Speaking for myself, I have had very good male friends, some I was vaguely attracted to, but since they were friends and I didn't want to lose them as a friend, I didn't think about dating them, until one of them, who I had thought about marrying in some very distant future, got married.
I had been happy as we were. oops.
I preferred dating people on the outskirts of my social circle so that when I stopped dating them, I didn't have to deal with it every day.
If I had been dating in college, I probably would have stuck to those outside the college or at least the dorm, but that isn't hard to do.
I don't want to have an ex- that I am going to have to let in to the building after his 3am date.
Living with someone doesn't really make them more attractive,( rather the opposite) but it does allow you to get to know them a little better.
I wonder if I am really unusual in that I preferred superficial dating for a while. I didn't want to delve into my boyfriends emotional goo. I wanted to have someone to go dancing with, that could teach me to work on my car and that would make my girlfriends envious.
I even dated a republican for a while

Cause he was funny & fun and gorgeous.
and he liked to dance.
But if I had lived in the same dorm and shared a bathroom with him- I doubt if I would have gone out with him once, because knowing that he read Soldier of Fortune magazine, would have put him out of the running immediately.
Still I think it would have been worthwhile to get to know him, and college life, including shared dorms can facilitate that.
I'd agree that young men have a harder time thinking of women primarily as friends and not sexual partners- then again I have heard that men have a hard time not seeing sexual imagery in everyday objects at that age.
My daughter lived in dorms for three years that were co-ed and had shared bathrooms. However- since each floor had two bathrooms, they had option to have the bathrooms designated by sex- they chose to leave them open to who ever wanted to use them, but if even one person had disagreed, they would have been single sex.
There are still womens' floors in most schools I have heard of , and while I can understand the point of view against co-ed dorms ( not rooms I think that is another thing altogether), I also think that men can learn to check their impulses and behave appropriately- isn't that part of growing up?