why?

Some time ago, a good pal told me about how he had come across problems in his relationship because of a conflict between the beliefs of those of his significant other's family, and his own. Yesterday, yet another close friend told me about how a blossoming relationship was faltering because of the very same issue. Now I may not be the best one to consult on this, and my opinion might not be the most correct, mainly because of the reason that I myself am not devoted to a single belief, but I always felt it wrong to let something so wonderful go to waste simply because I call my God by a different name from yours. Sure, in the end, one has to make way for the other, unless both parties decide to leave everything behind and move on to a more beautiful beginning, but sometimes I feel that looking too far ahead might not be the best thing to do in situations like this. And yes, you love someone, you naturally would not want to hurt his/her feelings in future when problems arise, but is making him/her feel miserable before anything has even started worth it?

Why can't everyone just get along?