The main reason is that there just aren't a lot of options for soft sleeving. Techflex and all the other industrial sleevings were meant for durability and easy of identification. Very few were made with aesthetics and ergonomics in mind. I have gone ghetto and tried nearly everything that had a removeable core to see if I could get a nice looking AND nice feeling cable. I hated the way Techflex felt.
For the most part if you want something nice and soft and are ok with only black, nylon multifilament is great since you can get it in any size you need. Otherwise you can try your luck with paracord (I haven't found any that fits over a whole braid), or microparacord. I discovered craft cord many years ago (which led to me finding and using microparacord), but craft cord doesn't seem to exist any more (too bad, as it was softer than microparacord).
Experimentation is what makes this hobby great. There is a lot of me too going on, even with the pros, but it is those brave souls who try new, sometimes ghetto things that drive us all forward.