Do NOT write this in stone... cuz I am not qualify to give you a 100% rock-solid answer.

But I would get the simple answer is FEAR. Fear of rejection, fear of being hurt, fear of mental anguish. Maybe you have a history of other people hurting you. Maybe your senses are telling you something, but more likely - you just do not want to be hurt again.

Relationships are always risky. But it is the risk/reward ration that you have to weigh. And only you can answer that question....

Good luck.