The mag mount antenna (almost every other antenna for that matter) uses an N connector, so you need the pigtail to run it into the MC plug on the card. Nobody would want to use a wireless PC Card with a 3/4" N connector on it
Except for (I forget who it is) "place name here" who posted before the great crash of how he modded a Linksys card so he wouldn't have to use a pigtail. He put an N connector on the card itself. Pretty neat. Anybody have info on that post?