I think it is depends on how mature is that person. I know some friends who got married, b/c they wanted to find partners for the rest of their life. so they picked the one that they can live with. since that person is not the one they deeply love. so they can give the other half more freedom and less jealous. more "room" for each other.
love the one that you can't live without, marry the one that you can live with ---less pain
i believe they just don't want to loss their freedom. also they can have child in their late 40s or even 50s, so why hurry to get marry wor
i think there is no unsolvable problem, it just depends on how much effort are you willing to imput.
if you decide to leave a person, you can just use whatever excuse.