Why?

Probably because it reveals almost nothing about the plot that was unknown

All it confims is that it is green goblin, not hobgoblin (most likely)

The plot of this movie is not unknown. It has been on the Internet for months, and the trailer, stuff, and else have confirmed it.

We've rehashed this too many times.

What I mean is nothing new about the plot

Yeah you are right, I misread it lol. My bad.

When does one movie poster say a lot about the plot?

^Hopefully, a poster does not say a lot.

Actually, it might.