I am aware of that. Also aware that there is thousands of duplicate accounts of same person. Probably around 20 % of accounts are dead accounts.
Others use trailing Upvote schemes. For example in my latest test I reach 260,000 accounts, spend about 15 coins, got 3 back after getting about 1230 upvotes and but my purpose was not getting back the money, but marketing to be read 📖 and get followers. I got I guess 1 or 2.
In spite of that at least some probability of being seen but not read.
In my view resteemers impacts better on marketing that Upvote Bidding Votes.
Rather distribute 15 coins among 18 accounts than give the 15 coins to just one bidding Upvote bot which takes your money, plus 25% from the reward pool. The 75% you get from the reward pool never matches or exceeds your 15 coins initially invested.
It is one and the reward pool the want being milked.