Most modern day adornments are not gender-locked. But yes, the old ones are- keep in mind ESO was in production since before TESV, so times were different in this media.
IIRC, people have asked ZOS why they don't just remove the locks and they explained it's not that simple because they made the mistake of hard-coding the gender into those cosmetics.
I think it is done to make designing process easier. Male / Female use different body & head models, so when something is being created it is most likely tagged as either male or female to prevent clipping / colliding. I would not be surprised if apperal item that can be use on both male & female would require extea work to create additional model.
I mean, even if the model seems to be the same (like earrings), it still needs different "skeleton" / positioning, so it would stick to head model in slightly different places, so it wouldn't clip.
Remember that they did just that for the Short Mussed Wave hairstyle - it was male only when it was made back pre-2016 (it started showing up on NPCs first in the TG DLC, but it's internal ItemID is lover than some of the basegame hairstyles).
The female and male skeletons do have different shapes, so something would need to be remodeled to fit. It seems easy enough to do, but if it works like the single player games (and ESO was in development around the time of Skyrim, so that's not out of the realm of possibility) it would need to get a new model added for the missing gender, which would need it to be reprogrammed from 'one model only' to 'one model for each gender' (or even 'one model for each race and gender option'). That means it would need to also get reprogrammed to point to the correct one (and there are even some that are messed up there - see why the female Khajiit morph of Unruly Bangs is wrong because it points to the female human instead of the female khajiit model.)
ZOS just hasn't seen the necessity in redoing older cosmetics. They've said things like they don't want to release the stealable clothes and the like since they are lo-res, but I do wish that meant they were better at releasing new things like hairstyles.
If it's because of different size/shape models and the potential for clipping it seems odd that there's accessories both my female breton and female khajiit can use, but a male breton can't, you'd think there would be more differences in head shape between races than two characters of the same race but different sexes. It also seems odd that it apparently doesn't affect costumes at all, when there's more difference in body shape than head shape (especially when, again, you factor in different races).
I suspect it's because of that rule they have about never updating released items unless they're literally broken. Originally they had some male exlusive accessories, some female exclusive and some unisex, then they gave up on that and made all the new ones unisex, but they won't ever update old items so they stayed restricted.
Edited by Danikat on March 13, 2023 3:00PM
PC EU player | She/her/hers | PAWS (Positively Against Wrip-off Stuff) - Say No to Crown Crates!
"Remember in this game we call life that no one said it's fair"
Don't know about adornments, but i want argonian male dance be available on all characters. That emote just freaking hilarious.
I would love the option to do all dances on all characters! If you can do the male dances on any character through some trick with toggling polymoprh, why can’t all dances just be made available directly for all characters?