For the same reason McDonalds is popular.
..having owned a Grand Prix which is basically the same car. I can say that it actually is good comfortable transportation that is pretty cheap and roomy. Of all the cars I've driven on a long trip, it was the only one that left me feeling without fatigue after 400 miles. I won't call it a great car, but I kind of miss it. But at 250,000 miles... it was time to hand it on to someone else.