[mediaqueries] Trying to understand the syntax design

Hello,

I'm trying to understand the reasons for the syntax design of media queries.
Are there any reasons why media queries are written "@media (min-width:
500px) { … }" instead of "@media (width >= 500px) { … }"?

I saw the document http://dev.w3.org/csswg/mediaqueries-4/, which seems to
also support the equal/greater signs with the following example: "@media
(400px <= min-width <= 700px) { … }", and I wonder why "min-width" is not
just "width" or perhaps "viewport-width" which it really is.

Kind regards
Lucas Wiener