Why do limited playlists exist?

I understand playlists like the “valantines doubles” one being limited, but why for things like regular “team doubles”? People like team doubles a lot and 343 just makes it limited.

It’s because of the limited population. I live in the US and I find it hard to find some arena matches sometimes…

To force the few players there are to actually be able to find games and play with each other.