E max on miss fortune

So I recently have just been shuffling through adcs, trying out all of them and seeing what works for me. Graves and twitch seem to be what I'm best with, but I generally like playing a third champ for each role.

I was looking at MF's page on probuilds and I notice almost everyone max's e first, and they don't even prioritize q at all (It's maxed last)

I understand that q already scales with your base ad, and w is really important because of attack speed steroids, but why do people max e on mf over q? It's an ap scaling, the base damage got nerfed even, in the early game when it's not maxed out it just tickles, and when it is at level 5 it's midgame and then you're not even doing much with it because you're an adc. What's up with this really? .-.