Audacious...or simply practical?

I was wondering. 

If two people are in love, and enjoy each other's company more than anyone else's, and it feels great, and they are happy to have found each other, then why it should be necessary for them to take their relationship to the next level and move in together thus risking to lose what they already have? I am serious. Why do successful couples feel compelled to start actually living together? Hasn't it occurred to anyone to keep on dating forever? I don't say that everyone should do it but the way I see it it's just as good an option and no one is even considering it and I don't understand why. Aging is mandatory and unavoidable, death is mandatory and unavoidable...but basically everything else is. It makes perfect sense to me not to fix something that isn't broken.

But then again a good part of what other people do doesn't make sense to me. I am pretty sure that's one of the reasons not only to remain single but also to know I am better off that way. Not better, period, just better off. That's not choosing the better of two goods, it's choosing the lesser of two evils. It's quite simple. Nothing is perfect anyway but it can be at least less complicated.