It's not actually always been like this; it did stack originally, back at launch, but there was an issue with this that resulted in an item duplication bug.Unfortunately the guild bank has always been this way in regards to stacking. Not sure if it will every change .....
If auto-stacking isn't possible because of this issue, then all that is needed is a Stack All button like you have in the personal bank and inventory. You'd just need to "lock" the bank for a few seconds while it processed, to avoid the duplication issue resurfacing.There is a reason stuff doesn't stack in the guild bank. It used to, but when it did, it resulted in numerous item duplication exploits. For example, if someone was in the bank trying to deposit a stack of 10 pots onto a stack of 15 pots, and someone else withdrew the stack of 15, you occasionally ended up with 25 pots in the bank as well as 15 pots in the second player's inventory. To alleviate this, auto-stacking the guild bank was disabled, and each "stack" is counted as a separate item.
I have played on XB1 since launch, it has always been this way on XB1. There are multiple platforms, I dont keep up on information prior to release on XB1. Sorry for the incorrect information, next time I will keep my mouth shut instead of trying to assist and let the Community Ambassador assist everyone .....