Whether someone increases their Steem Power holding through rewards or powering up is irrelevant - their votes will still carry the same weight
It is relevant when you put forth theories about who is gaining or losing share and why. Are dolphins gaining due to rewards or buying in (powering up of SBD is some combination of these two)? Is the slowdown in orcas due to a slow down of reward earnings or have they stopped investing or increased power downs? These are all interesting and relevant questions. Not disagreeing that just the distribution numbers on their own are potentially important, but many times they raise more questions than they answer.