As is evidenced by this forum, someone will complain about everything. That's hardly a tick against it. If enough people complained it could be adjusted with a larger range of "basic" job glamours such as making them change every 10 levels or so or have palettes of possible combinations. Every single possible problem doesn't need to be solved for something to happen.
It would absolutely make lower end computers bog down less when loading in crowded areas. Fewer textures and models being loaded = less demand on RAM. How significant would remain to be seen but many of the games I play who have this type of option do it for optimization of loading in crowded areas.
Another benefit you may want to think of is people who complain about not being able to identify jobs by gear and use that excuse to argue for limiting glamour options will have an option to hard-limit other players on their screen to easily identifiable models and textures.
No more "we need this gear to mean this job/class/race" excuse.
Every option and suggested addition is people who aren't satisfied with the way it is. Their reasons are their own and you not understanding or believing them doesn't invalidate them.
They do this all the time when they make graphic fidelity adjustment settings or allow you to skip cutscenes or make optional content. Is all of that rude?