"...vPIXEL is a spend-only token so we can give it out as reward and you won’t be able to sell it on an exchange...

...I can see the PIXEL token becoming stake-only. We probably will even phase out rewarding the token in the long run and essentially stop emissions and just have the token be stake-only."

https://www.blockchaingamer.biz/features/interviews/40807/luke-barwikowski-pixels-make-play-to-earn-work/