I am very curious as well.... They probably don't care how much they will earn if they upvote themselves because they are they creators and they probably don't need to spend 1 hour posting for just under 10k.
However, you are right if that SP could be used to help other in the platform, it could be awesome. Perhaps they have a reason for not doing so, I can see that a lot of people already asking that account @steemit to upvote them (its wallet history have lots of people sending fragments of a SB and asking for upvotes).... I think the steemit platform etiquette guidelines says try not to do that beg for upvotes.
I'm not proud enough not to beg an upvote from a Giant like @steemit , when in fact an upvote from him would not affect his Power... I guess etiquette is just a guideline but not a rule.