You know what's funny is that they tell you to power up but they are powering down all 3 accounts and cashing out $2 Millions every week.
I don't know what the founders are doing with their personal accounts but the steemit account (by far the largest) sometimes powers down and sometimes doesn't. No one is "cashing out $2 million every week".
They do this to create liquid steem that is used to fund new accounts (2/3) and is sold to fund development (1/3). So far on the latter this is their only source of funding (there was a small angel round a while back but I'm sure that is long since exhausted).
When available liquid steem is sufficient they turn off the power down (which makes sense to preserve wealth). It has been switched on and off a few times now.
My guess is that with the high level of exposure and high demand for new accounts, the need for liquid steem is high and power down will stay enabled, but I haven't seen the numbers so this is just a guess.