Most Helpful Girl
To have a wider 3D range of vision so you don't need to rotate your head significantly to see one side or the other.2
Most Helpful Guy
The origin of bilateral symmetry in general seems kind of inconclusive. I was glancing at a paper in response to this question suggesting it has to do with cell replication at a molecular level, with one parent cell yielding two symmetrical daughter cells -- it was a bit over my head, not a biology expert.
Definitely there's an evolutionary advantage to having two eyes, but likewise there might be for having two. Why so many organisms in the animal kingdom have bilateral symmetry is somewhat of a mystery. I don't think anyone has a perfect answer.
In general, nature has a lot of symmetrical systems -- radial, bilateral, etc.
Just kind of in layman terms, I think it's somewhat beautiful in this regard, like there's a simple formula which gives way to replication which yields symmetrical patterns, and perhaps even some level of redundancy (but redundancy isn't necessarily useless).0