as usership grows, the amount of people fighting for that rewards pool grows and grows each day, and each person controls less of the rewards pool.
Each person or the average person? Certainly, on average, people will have less access to the rewards pool. But those who are accruing Steem Power now will be in a much better position to control the distribution of rewards in the future.
I meant each person. Nothing stops a user from buying the liquid steem that exist on the exchange. But in the game of numbers, each person might as well be considered the common person, or average as you put it since very few will have that ability to do so. I purchased my steem power, so I guess i would fall outside the average person.