Because they're not really socializing with each other. They need another world in which to exist in order to socialize with each other. Therefore, if left without computers, how would their relationship work?
I hate to tell you this, but real world relationships between adults aren't so idealistic.
I dont know what kind of people you know, but many normal couples, 1) have fights, and 2) enjoy things that are considered "weird" or "psychotic" by others.
As long as there isn't any abuse, no body has the right to point fingers at antoher couple.