When voting for yourself, 100% goes to yourself. It can't be any higher than that.

What matters here is the balance between the alternatives. Both 50% and the current 25% are clearly still less than 100%, but 50% is a lot closer. Therefore balancing the incentives becomes more within reach at 50%.

A more extreme alternative would be 90%. At this point the benefit to self voting is only 1.1x and far less likely to be worth it. We'd likely see hardly any farming/self-voting at that point because it wouldn't be worth the risk of getting your trash downvoted for that extra 10% when you could be an average or even slightly below average curator, find some non-garbage and go vote on it.

We're in favor of 50% because (unlike say 90%) it is a moderate and the pain in terms of author reduction is relatively modest (33% reduction) relative to the increase in curation (100% increase) and therefore it is a number that has a good "return on investment" (using that phrase figuratively) when it comes to shifting of incentives.