Fun and humor makes up parts of Meta Stack Exchange; I'm not sure how anything else would be on-topic. Several other non-functional chat rooms exist on the chat.meta.stackexchange.com domain, such as:
They're not necessarily discussing about the major policies of the Stack Exchange network, but that doesn't make them off-topic. Discussions should be allowed. Otherwise, over half of the rooms are going to die (excluding the Tavern because we cannot live without it):
The faq also says:
Do have fun, but please keep it professional and always be respectful of your fellow community members.
The rooms are not becoming a problem (generating offensive or problematic discussions), so there isn't a need to remove these rooms or discourage discussions. Moreover, the room is also roughly on-topic - Meta Stack Exchange discussions do occur occasionally. For example:
I cannot delete that answer because it's accepted.
yeah, the OP said it's all good didn't you see? That's why I didn't comment any further