Guide to Make Leather
When the raw hides are on the ground manually instruct someone to haul them.
For myself the auto use of the dryer would not happen until I did this.
After I did this the auto use of the dryer was fine. I had hides showing on my list of items but could never find them in storage anywhere before I did this.
Might be bugged or maybe I am just wrong and using the dryer for hides after I did this was just coincidence but it wont hurt you to try.
Hauling hides seems to be very low on the priority list. Like your people will literally do anything else first before they start hauling hides.