Happening to me, too. I'm all for them enabling autononomy on the workbench, but currently it is way too attractive to every Sim. Doesn't matter if they have high or low handiness skill. If you really want to see this issue in action, make a household of eight and put them on a fairly large lot with many other things to do, and I can pretty much guarantee one of those eight Sims will always be on that workbench unless they're all asleep. I don't think it's about them not having anything better to do, since as I said I really saw this happening a lot on a large lot where the household has many other things to do such as computers, TVs, stereos, a movie screen, instruments, games, you name it.
I finally just got rid of the thing because it was causing inventory pile-up on my Sims. Some of them seriously had like 40+ sculptures in their inventories when I checked.
I'm cool with them keeping this item autonomous, but it really needs to be toned down a LOT.
Edit it to add: Happens with or without mods, doesn't seem to be related to any particular traits or emotions, and in my game at least they weren't neglecting their needs in favor of woodworking, but the game does seem to push them to do it frequently which can cause some queue-stomping.