Few steemit users think that using bots for getting upvotes is a bad idea because even if they return the same amount of SBDs or even a little bit higher, they will be redeemed either to 100% SP or 50:50 scheme. For those I wanna say, to be successful here, you must focus on your SP, through bots, you get extra steem power as compared to if you convert your SBD's directly into SP. Though you cannot be cashed out in the short term, you'll surely end with good terms in the long run.
and yes it could be one of the reasons for SBDs value to go up. Good analysis @exyle.