It was you and @tarazkp that pointed me in the right direction, but thanks!
Looking at what behaviour on steemit can be characterised as rent-seeking is really important, because rent-seeking is generally considered to be bad for productivity and growth within economies.
When rent-seeking is too easy a way to earn money, investment in production and innovation falls. We see this here, as people move away from content creation and manual curation in favour of investing in bidbots to generate passive income.
If the economy has enough diversity and overall strength, this might just skim a few percent off GPD. But if too much money leaves other parts of the economy, it can't end well, because modern economies can't run purely on rent-seeking. The equivalent here would be if so little new content was produced that seeking rent in the attention economy no longer paid a worthwhile return. I can't imagine that such an end-point would be very pretty.
Even as a newbie this is something I noticed about Steemit quickly. Most new non-Steemit themed content received few views or upvotes. Other content that focused on how 'to play the Steemit game' seemed to get many views and upvotes, even if the posts were very short. So many posts trying to sell bot services, or explaining how to use bots etc. If this continues, it seems to me Steemit will end up being a platform about itself, a mirror pointed at a mirror sort of. New content creators will have fled. As a newbie, I have the distinct feeling that if I don't pay for a bot, I will forever be invisible here. Time will tell. Thanks for the very useful comments and observations.