As far as GPL goes [...]  Remember, I'm talking about firmware
      here for embedded systems or controller cards.  The source code
      does not benefit the end user at all

   While that may be true of most end users, for many it's not true.

As any example, I would love to reprogram some modern terminals to
have the meta keys that vendors seem to always forget.  I'm still
using more than one Ann Arbor because of this.