I’m not sure any store can allocate part of their budget on ‘try on’ pieces for such popular items. These popular items are relatively entry level in comparison to the bigger pieces, so there are many more of them (think rings, bangles, bracelets, small necklaces, and every variation of watch one can imagine.
I agree with the post above that stated if you truly cannot be happy about the possibility and cannot trust the SA even if there are no signs of use, then perhaps refrain from purchase. The flip side of a client demand that a piece never be tried on is not only to refuse a test drive but also make every item final sale, not returnable.
I was at a Tiffany event where my SA pulled out a signature high jewelry piece for me to examine. I’m sure if a client of hers was seriously interested in purchase, she would have been able to try it on. And, I don’t think that this would have been an impediment to the final purchase.