Threads naturally die when there is no more discussion to be had - do you think that time is an hour after the game?
If you post just after, go to bed, login at work to reply to someone...its locked.
Why do you care?
People get wound up about weird stuff here.
It’s just a way of managing the large numbers of threads on there. If people want to keep talking about a game there’s a group thread they can go to. The threads tend to be locked around midnight because the matchday is over. It’s not difficult to find the right thread if you still want to post about games. It’s very much the purpose of the group threads to allow discussions about matches and teams throughout.
The forum is moderated by volunteers who have lives and jobs, if it makes things marginally easier for them to manage the subforum (which is set up and run for the convenience of users) then so be it