Cohabitation and Christianity/Catholicism?

I've noticed more and more frequently that it is becoming the 'norm' to live together before marriage amongst Catholics and Christians. How is it that people can find this acceptable when their beliefs speak to the contrary?? I'm only 27, but I remember when integrity and not compromising ones beliefs meant something, but now adays the excuse for this behavior is 'times are changing' and/or 'thats old fashioned.' I find it harder to understand how people can live so contrary to that which they claim is dear to their hearts. I understand no one is perfect and we all have our thorns in our side, but I dont understand how someone with these spiritual beliefs can find it so easy to compromise and not see anything wrong with this. (This is even very prevelant in the entertainment industry with musicians and even actors - which is probably why many people see it as normal behavior.)