Is easy to say "just get together", but I have seen a couple of...couples that might work together at times but they were holding onto their marriage just out of convenience, either economic factors, or loneliness, people that would hurl insults at each other or even cheat on each other.
Another that still hasn't gotten fully over it, despite how it just wasn't working out, cohabitation is a hard challenge and if your partner is not willing to change his/her bad habits you didn't know before, is gonna be hell.
Some people have flaws, they might know it, but don't want others to remind them and won't ever change.