Why people do relationship when they are not ready to accept partner bad sides?

I mean you can't say hey listen I only want your good sides of yours. I don't want your bad sides. Bruh you're in relationship accept her as she is or leave her same with guys. Your thoughts?
Updates
+1 y
Although I don't believe in relationship n love for me it's a scam. This question pop-up in my mind while talking to my friend. ✌️
Why people do relationship when they are not ready to accept partner bad sides?
Post Opinion