The real reason is in the post:
Each upvote "prints" V-shares, causing the upvoted post to get an increased percentage of total_reward_fund_steem and slightly decreasing all other posts' percentage.
By the way, although I think this post is very good, in order to encourage new users and/or articles/blogs which are not about Steem/blockchain, I won't up-vote it (which will decrease other posts' percentage of total reward). Sorry.
So, your curator reward is lost.
No, from a strategic voter's point of view, I'll save up my voting power so can use it elsewhere, and hopefully will earn more reward.
Isn't the exchange rate a factor too? It has been declined quite a bit recently.
Yes it is.