I don't think that people living togther before marriage is necessary. Apart from the whole "no sex before marriage" thing, which living together would strongly encourage, the only other reason I can see for living together is to get used to taking care of a house together.
Personally, I believe that the relationship should be strong enough to withstand the rigous of living together and looking after a house, even if it's so extreme that both people both hate the way each other does everything around the house (and strong enough to withstand the possibility of one or both people not being satisfied sexually.) If a couple doesn't think their relationship can survive the prospect of them being annoyed at the way the other person does housework (or the potential lack of satisfaction with sex,) then I don't think it's a strong enough relationship to base a marriage (and kids) on, and therefore not a strong enough relationship to involve both couples living together. I don't judge people who do live together before marriage though, that's between them and God.
Anyway, it's not like people can't discuss and prepare to deal with each other's various methods of house-cleaning before they get married.
That said I'm entirely in favour of people learning to cook and clean etc. before they get married, whether that's achieved by taking on repsonsibilities in one's parents' house or moving out with friends.