I don’t agree that there is no purpose other than it’s fun.
Actually, a lot of the time it is not fun. A lot of the time it is “whhhhyyy do I play this game!?”
I play it for discipline (mental) and learning. I play it for stimulation (mental) and protection against the aging mind. Etc.
The answers in this thread cast more light on the deeper reasons we play that can’t be described as “fun”.