I do not think most users on Steemit vote for the curations rewards. Curation rewards are for the small SP holders next to nothing and they must realise this quickly looking at their weekly curation rewards versus weekly post and comment rewards.
And if most of the users would vote to maximise their curation rewards, they do not seem to have the correct knowledge in how their rewards are maximised. It seems that posts with a lot of votes and a lot of rewards will automatically attract even more votes. Users vote for HOT and TRENDING posts. But in fact, the result of such votes are minimisation of their rewards, unless the votes are casted as one of the first, before the big fish casted their votes. And even then, the rewards can be quite low for a small SP holder of which we probably have 99% of in our community.
But actually, I think most of the Steemians do vote what they like, instead of thinking "will I maximise my earnings with this vote?". And to be honest, I would love it when most of the users would indeed only vote for those posts that they read and really liked. The vote slider can be used to express how much you like the post, 100% for awesome and 1% for "I somehow like the post, but somehow also not, but I like to support anyway" or whatever reason it is for a 1% vote.
Thanks for that detailed reply, much appreciated. Agree that as newbie with near to nothing on SP the ROI aspect is not relevant. Personally I try to find a way to vote for both. The Whales might see this different as they might have invested some real money.