The biggest utility is being able to make spare parts for things that are incredibly hard to find, vintage Seikos come to mind. An SLA printer would be a huge asset to a clockmaker. I don't know all of the ways a watchmaker could use it, but being able to print out custom movement holders on demand, complete with pushers built in for chronographs with zero assembly required can save quite a bit of money in the long run.
Have a stubborn case back? Well 3d print a nylon rig that engages all the notches on the back to open it with zero chance of scratching it. You can print custom spacer rings on demand for movements too, and also any kind of tray or dust protector you need. It's a very useful tool in many areas.