How do you ask someone to power up $1M worth of Steem (a high-risk investment) and then expect them to give almost all their rewards away.

If earning less STEEM would lead to a higer STEEM price, I immediately would agree not to earn any single STEEM anymore ...
If supporting others and make them grow could extend the user base and thus make the whole blockchain more attractive for investors (who may only think it's worth to advertise and try to sell theirs products on a platform with a sufficient amount of active users), then I wouldn't actually call it altruistic doing so ...