I have quite a few reasons for my Jag-Stang....
First off was the Kurt Cobain connection. I may shred now, but before I got into New Wave, Hard Rock, Hair Metal, Thrash Metal, and yadda, I was into Alternative/Grunge (and before that was 80's synth pop scary enough). When I heard the Jag-Stang was coming out I was hoping it'd be cheaper than the reissue mustang so I could at least have something "like" a Jaguar and Mustang, and maybe "fill in the blanks" per se to build my own Jaguar, while having the other guitar on top of it. I played a Fender Prodigy with EMG pickups around the time the JS came out, and liked the pickups, which I found the S-coil EMG's bore a resemblance to Mustang single coils. So one day in school I was bored, and decided I wanted a Jag-Stang with EMG's.
Making the second one the fact that I did not have to pay extra to have the EMG's installed. They reduced the price of my JS because it was modified (EMG pickups and different pots, plust they were not installed right, which I could fix). I also bought it because of the neck, as it's one of the MOST comfortable necks I've ever played on, as well as the trem being shockingly stable. At the time I was playing lots of Van-Halen, and found the trem was pretty stable to start with, despite the fact I was not using the bar but pushing the "cigar tube" thingy forward with my palm for whammy stuff.
Needless to say, it was a mixture of tEh KurDtZ, having EMG's pre-installed (hence looking more like a souped up Mustang in the electronics department), a Tremelo that stays in tune, and that I got it for cheap due to it being modifed roughly. It also only sold to me because I recall there was a trick to get the patch cable in it (because the battery would slide under the input jack and block off the patch cable), and I was maybe one of very very few people who figured that out.