Question

why people have two eyes

Answer 1

I have two eyes to see the nature and everything

Answer 2

Having two eyes enhances depth and 3-D perception by a process called stereopsis, which involves parallax. Parallax is the effect we see as we move past objects and objects in the background appear to be moving slower relative to objects closer to our eyes. Stereopsis gives our brain two different overlapping images that's processed with information given by parallax. If you close one eye, you still experience parallax if you move your head, but you will notice that your depth perception is not nearly as good. 

We don't actually see 3D, but a pseudo-3D that is much more 2D than 3D. If we truly saw in 3D, we would see an entire three-dimensional object at once.

Because we move. Successful navigation depends on having effective sensory apparatus. We had to protect ourselves against other animals that could navigate well. Luckily, we shared a common two-eyed ancestor with many of these animals, and so we had two eyes from the start. If we didn't, hopefully convergent evolution would have brought us there... or here.