Quite the opposite. Comparing anything with net pay is pretty pointless. Your total tax rate depends on many factors: total household income, number of kids, deductibles, filling jointly or separately, etc. Plus, the exact amount varies over the year, depending on how much you've already contributed in sales and federal taxes. On the other hand, gross pay is a single, round, fixed number.
I understand this may sound a weird concept for people in some countries outside the US, but it's a much simpler concept once you get used to it.
To continue off of what guiambros said, unless you get no refund or bill come tax time every April, you don't know what your net pay is until Q2 of the following year.
