DISCLAIMER: Self-voting is a personal preference.
I always vote for my posts myself. It was default back in the days that you vote for your own posts, until it was considered sub-optimal because of the reverse-auction anti-bot protection during first minutes of posts' life.
Actually enforcing self votes at the blockchain level could bring interesting counter-intuitive results; those who will spam with posts looking for rewards, will strip themselves from potential curation rewards, as most likely not only their self votes will be countered, but also there will be no voting power left for other "safe bet" curation reward targets.
I don't much like the consequences of your theory, so when the next hard fork arrives, please get distracted listening to 'Kahsmir' if this enters your head.
Speaking of.., are we going to have another HF, it's been a long time.
:-D
Well, when it comes to HF, there are no pressing issues to be fixed, improved by the HF, however we have lots of small HF-required stacked and idk, as always - matter of consensus. The most problematic thing about HF is that it has to be coordinated, accepted and deployed by the exchanges, and as much as we all love upgrades, it has it's non-zero costs (time/effort) for all interested parties. We will see how things goes in Core Dev meeting tomorrow.