The problem with that is, the pool is fixed. The inflation would continuously shrink your individual share of it. Under the current regime there is competition for this fixed resource, which is absolutely the way it should be. What you suggest would dilute it down to nothing. That's what enforced 'equality' does, it makes everyone equally poor.

Publish0x uses more of the fixed tipping model you are describing, but the reward pool is provided by projects and advertisers.