I'd rather be single than have that. My sister has a weird couple as friends, they're always so hostile and sarcastic to each other, constantly arguing. Why anyone would stay willingly in a relationship like that is beyond me.
A lot of people never had positive role models when it comes to sharing their feelings.
When I started dating my now wife, she would sometimes ignore me for a week if we got into a disagreement, just because she couldn't tell me what's bothering her and be real with her own emotions.
She's grown a lot since then and when there's inevitably a new argument we can resolve it very quickly now.
Communication is important, but it's something you have to learn.