Since the hardfork and the economic changes, buying votes from bid bots gives you a profitable vote cause almost no one wants to use them for actual promotion. It's more about the profit they make than you and to discourage people to send them Steem + the curation rewards they make we are downvoting authors using them.

If everyone bought profitable votes the ones not buying them would lose out twice as much at the same time those curating without selling their votes would also lose out on a lot of ROI compared to those delegating to bid bots receiving both curation rewards and bids. The owners are of course taking a cut all along the way so they don't want this "business" to end.