I think you left out a category of tyers that sell their flies...

The concept of the Hindu cow always makes me think of the fulldress tyer that won't fish his flies, or worse, the tyer that never leaves his bench to fish any flies. I enjoy tying flies and lots of flies are not available the way people want them tied. I get all sorts of requests to tie non-conforming, elsewise unavailable flies. I do it because I do not revere my cow so much for all the things it could do for me that I will not avail myself of those things...