In the shop, no, tubes are not worth patching as we would need to charge customers more to patch than to sell them a new tube. Do a patch wrong and the shop would be out even more money.

Currently, I have a folder running presta valve 18" tires -- general unavailability of tubes for this system means I patch tubes.

And generally speaking, I will carry a spare tube, swap it out in the event of a flat, and then patch/repair at home. Sometimes this happens; sometimes a heap of repairable tubes eventually just gets thrown out. How valuable is your spare time...?