You must be kidding: ...
I am not, I am sure that witness pays fees:
One way to become a witness is as follows:
1. Run the witness code on your server
https://github.com/byteball/byteball-witness. To be considered seriously, you need to run it on a server that is well connected and always online. Running this code alone won't make you a witness automatically, you'll just periodically post your units to the database (and
spend your bytes by doing this).
This is when you try to be witness. Once you are witness included in the 12 witness list you don't spend you bytes doing this. Stop spreading misinformation.
AFAIK, witness needs to submit transactions all the time to confirm user's transactions and he pays tx fees. If payment he receives is larger that fees he pays, good for him.
Witnesses will never accumulate all bytes, because if users have no bytes, they can't submit transactions, hence no fees go to witnesses, therefore it is in their interests to sell some bytes on the market.