Some people are marriage material, while others are not. Even if someone wanted a marriage that doesn't mean that they are suitable for married life.
Married life requires having discipline, consistency, and resilience. Those who are prone to emotional and mental breakdowns, difficulty picking back up, get bored easily, develop addictions to avoid dealing with issues - just to name a few things - are not marriage material.
I haven't even touched upon what kind of financial habits and perspective about money that one should have in order to be marriage material.
Of course, ANYBODY can get married but that doesn't mean the quality of their marriage will be any good or bear fruit. However, there are plenty of couples who are okay with getting by because they have developed comfortability, familiarity, and co-dependency. In other words, whatever floats their boat.