The reason why we have two eyes is so that we see things from two different angles, thus giving us depth perception. In other words, we see in 3D.
No we don't... You can only see 2 dimensions, up and down, left and right...
the 3D effects can be a plus if they don't cause headaches/other pains or if the person doesn't have vision problems
People are probably Nwing this because of the whole "Humans can't even see in 3D". Seriously, we can't. We don't see a third dimension, we only see two, left and right, up and down. We can't see forward or back, we just assume that something is because of the shading that is left or right.