Sometimes it's impossible to see clearly with only one eye open.
edit - Alternatively and with some expansion - with only one eye, you get a flat view of the world, possibly distorted if you have an astigmatism. You may also have a problem with perspective and judgement. But if you're content to walk around with only one eye open, then...
...you're probably an extremist or a Republican.
edit 2 - Don't always believe what you read on the internet; it frequently is written by someone with only one eye and transmittal of one-eye-disease is quite possible.