I can certainly agree with you that no one would pay to volunteer - unless substantial opportunities to profit through other means are potential from the position. Given the influence these positions are going to have over lots of aspects of the blockchain, I hope, there does seem to be substantial potential to influence mechanisms that could be highly remunerative.
We want it to be 'solely meant for the universal benefit of the Steem ecosystem and blockchain', but there are demonstrably folks hereabouts that have no concern for anything but their money. I do hope that the foundation is able to exclude such, but I note that is a faint hope if examples of well funded foundations handling fiat are not more ripe for corruption than Steem's foundation.
I am confident that folks with pecuniary interest will be carefully examining these positions for any potential to profit from them. Assuming no one will seek to do so isn't reasonable. I may be cynical and paranoid, but not without reason. I hope I am less cynical and paranoid than you.
...for cynical and paranoid, read 'life experienced', and not naive