I'm speaking particularly of the purely-decorative ones; or the ones added to up the "jewel count" to some nice round figure for sales. I doubt that those have any positive impact on the functioning of the device.
You won't find many manufacturers (if any) that use jewels in the movement for anything other than efficiency purposes. Rubies are actually one of the most low friction natural materials known to man, so watchmakers have been using them in movements for a long time.
Only recently have we started seeing more advanced materials/alloys being used in lieu of Rubies.
I think you may be referring and responding negatively to decorative watches found in fashion stores typically sold for a few hundred dollars. The mechanical watches discussed here and in the original article are in a different universe.
Woah, you don't know much about watchmaking do you? Can you name one single respected watchmaker that adds jewels to increase "jewel count"? Hell, not a single haute horology house advertises how many jewels they have in their movement. They simply label it, and you won't see it in any marketing material because it's irrelevant.
Jewel inflation used to be a big thing in the 60s and 70s, with watches advertising 70+ jewels,most of them completely non-functional. These days there are standards on how jewels can be counted and it doesn't occur that much. It's mostly only done by the cheaper brands.
