Well, you mentioned point (2) on flagging for excessive rewards, and that's the main upside, as mentioned here.
Regarding curation, you are quite wrong about that, and in fact I feel this is something that more people should be aware of. You get back 1/8th of your value even if you vote last (and the curation curve is designed for preserving a minimum incentive to curate). Of course, you can say that's a garbage amount, but it's quite crucial, because as you say, a lot of people are under the impression that after the votes are done there's no reason to vote on top. And that's just not true.
But right, that's not relevant to 50/50 at all. What it is relevant to is that it gives more motivation than before to curate vs self vote. Obviously some people will prefer to be lazy, but the way things are designed, curating really gets quite a boost (especially with the curve).
That is a point that I and no doubt most others miss about the curation reward system, otherwise there would be more individuals like me that vote when we see, read, or enjoy the post regardless of when the post was made if it is in the seven day window. Most post never receive secondary votes after 36 hours of being posted.