Lots of jobs do come with a sartorial difficulty level above absolute zero. Not all jobs, but many. Particularly for women (which would be a whole new can of worms we better shouldn't open here)

A widespread low-but-definitely-nonzero would be that you can absolutely wear what you like, but half of the informal roles that are within the scope of your job description are effectively closed unless you dress the part.

Why would that be defensible or desirable?

The blog author comes across as fetishizing that shallow, expensive, your-opinion-dictated-by-fashion, world.