Proof of Brain is how the blockchain platforms are designed to reward. Today I believe it doesn't work like expected mainly because too many never use the right to vote which is only a question of hitting that button - a minimum of 10 times per day. The higher the SP the higher the vote but also the more one can vote (different people can benefit).
So if no one comments and large number never upvotes it won't do the PoB system any good (see the whitepaper of Steemit).

I the case of marketing I understand that the client is most important but,, that client pays for a certain service. It's not that he receives your idea for free and gives a vote (fee) or not.

In this case we all use a system (a plan, idea) and benefit from it even if it's little and if you can do this for free with a chance to generate an income (we both can but many others can) I do find it normal to invest in what keeps you alive.. investment in this case by upvoting and commenting. (I don't talk about buying Steem) just those simple things anyone can do.

The same for voting for witnesses and proposals. I understand many are too difficult to understand and not written for the average Steemian, A change of approach, connecting with the voters wouldn't be a bad thing, although it's all very time consuming,