That's funny, there's lots of things I hear where people are like not sure why but its best to do it this way, but don't quote me on that lol. It is kinda confusing and overwhelming at first.
I guess the reason for my question is if I vote on something that already has 100 upvotes it's already popular but I thought there may be some incentive for spotting something you think will be popular before its gotten popular
Here's from the Steemit FAQ
How is the reward pool split between authors and curators?
Up to 25% of a post's payout is awarded to curators (the people who upvoted the post) as a reward for discovering the content. The other 75% is awarded to the author. If curators vote for a post within the first 30 minutes of it being created, a portion of their curation reward is added to the author payout. This portion is linear to the age of the post between 0 and 30 minutes. Therefore upvoting at 15 minutes old will donate half of your potential curation reward to the author.
Interesting to me, this says the opposite of what I said, that it's better to do it right away!
I read all these things and the reasonings behind it just don't stick with me. Haha