well the thing is, the more steem someone holds, the more steempower they have, so they basically see self-voting or delegating/selling their votes to a vote bot service as getting a return on their investment. Then they plough their sbd/steem rewards into bots to gain further profits. Steem is just like any other crypto at the end of the day where the big boys are looking for big returns.
RE: 25 Reasons Steem Will Replace Bitcoin as #1 Cryptocurrency by 2021!