I think it's just because they don't want to let on that their content isn't actually being upvoted organically. Not because they think it will lead to people actually using the bots.
Case in point, I've pretty much laid it out for you guys in this post how to get to the Trending page using paid upvotes/resteems, and I'd be willing to bed that none of the people who read this actually use my method the way I'm describing it.
Part of it has to do with spending the money. Most people probably don't have $1200 to spend on their vanity on an experimental blogging platform.
Actually, I fucked up the calculation... it's probably closer to $3600. Whatever. People aren't going to do it anyway.
I have tried to use bots in order to get into the hot section, it worked, I have not really calculated the ROI, but I don't think I lost money so far... Not sure if being on like 17th place on a list in a obscure "hot-section" gives much more exposure...? When I have some more "cyber-cash" I am going to try your formula to get into trending... Thanks a lot for the post it was very helpful.