because you like to play.
Why is chess fun to play?

Some people hate chess
Some people like to fish, others like to run. Some people like to drink.
Why does anyone like anything?

I hate running. I have low red blood cells count. Just saying that some people like some things others like others
Some like math, others hate math. Some like reading others hate it. Some love school others hate school.
Such is life.
Everytime when I play chess with a person, something just makes me happy, feel relaxed and entertaining to play. Is there a reason why that happens?