but at a /join it should be refreshed imo

I dont agree....
There are many commands that could be sent on join
Some networks dont display topic/mode information when you join, so they have to be requested... none afaik send ban or /who information... and I'm sure that none send +I/e info...
If bans are going to be retrieved, what about /who to update the IAL? what about /mode +I or /mode +e to retrieve the other lists?

All that adds up to is a LOT of lag right when someone joins a chan and expects to do something (such as request for ops)