What usually are the reasons that makes human imperfect?

The reasons that makes human imperfect are we have sinful nature, negative thoughts, poverty or unemployment rate is high, we all die in judgment day of God. We have to accept our sin & salvation in order to be perfect.

I believe it's because all human beings are different. What I would perceive as perfect, somebody else may not. Also, because we are different, we think about things differently, and behave differently. Sometimes, the things we do that we see no wrong in, somebody else may disagree with entirely.