Since the last update in Classic:

-the stack count doesn't show in tooltip anymore (to show how many of an item you have in bags and in bank
-the bank is empty when right clicking to toggle your bank when you are out in the world

+1 Here. I thought it might have been related to all the garbage that Auctioneer adds to the tooltip, but it doesnt seem to be the case. Just don't have any inventory counts anymore.

Enable BagBrother

I have this issue too, and BagBrother is enabled.

Edit: I had this issue. I appear to have just fixed it. Originally, I played Horde side in Classic and recently switched to Alliance. Alliance side had never shown the BagBrother counts at all.
I logged into my Horde character just now, the counts were shown as they always had been. I logged back into my Alliance character, the counts were now there. It feels like the Horde side character data needed updating or kicking in some way, and was preventing other characters from working somehow. I haven't investigated the code, nor did I think to keep a backup of the BagBrother SavedVariables before doing this.