Why are people cruel?

Not all people are cruel , only some people are cruel .

So many reasons. Everyone us has been cruel to someone sometime in our lives. Maybe we didn't even realize it. It's in our very human nature to be cruel. That's why we have to fight against it every day. Sometimes you win the battle and sometimes you lose. But every day you can start fresh with no mistakes...yet.

Because I deserve to be cruel to when I am just alone?

Heartless

It's kinda like the game "hot potato" that game you were taught when you were a kid, teaches you to pass your problems thus being the "potato" on to someone else so that you aren't being burnt.

Because they've never had it hard....they simply don't know what its like....

Because they are unhappy, and want to spread their unhappiness.

Cuz they are determining it to be better than the alternative through their choices.

Because Satan is still in the world .

Probably tired or miserable.