Why ? 

Without mentioning NASA and other space agencies.

This is not a joke thread im just curious

Cause school

If earth was not a ball then the real life "draw distance" would be way too big. Plus from plane you can actually see how earth horizon looks like. So that's what I would have said to defend the "theory" of earth being round (earth is not perfect round though).

That is because when I was a child a teacher taught me that the earth was just like an Orange. :P

I don't really get the question?
It is what it is..

Gravity.

There's a whole stream of things I could say to answer this question, but the most obvious one is often the best.

Because it is.

polution is a big issue so you cant see really far and as for planes it looks like theres a curve because of the windows.

This.  The fact that you can leave from one point and travel in a straight line returning to that point without "dropping off the edge of the world" proves the Earth is spherical.

Lol.