Why Close accounts
Perhaps because it is a clean break. Everyone can see that the account is closed so they don't waste time sending messages to someone that isn't there. Also wondering why they aren't getting a response back. And also wondering why that person hasn't been posting. While one can make an announcement in a forum, that does not mean everyone is going to see it. Just a guess on my part though.

In regards to people closing their accounts to avoid gettign closed for fair play, that seems like a possible way for someone to cheat and then not give people their rating points back because you dent gets points back for self closure. However this may already be addressed by chess.com in which case there's no issue.

I've seen people close their accounts to avoid them being closed for fair play violations
True.
@YouEvenLiftBro didn't close his fast enough

A person i played daily games with four times
i asked for a rematch. But realized he closed his account…
On January 3 he won a game the next day he closed his account. I am still very confused to this day…
he also had 3 daily games running all of which he lost on time due to him closing his account…
it’s just very weird.
any ideas let me know!
Why do people close their accounts? Why would closing your own account for inactivity matter if you are going to be inactive and not come back?
Why close your account what if you want to come back and can't get the account back?