The only cars I have seen designed with a shorter track than what was possible it was because of aerodynamic reasons (touring cars). A wider track would put the tyres directly against the airflow.
Another reason may be (although I havent seen) in racing cars that have to go through narrow roads, like autocross for example and a shorter track can help a bit while negotiating tight chicanes.
"You need great passion, because everything you do with great pleasure, you do well." -Juan Manuel Fangio
"I have no idols. I admire work, dedication and competence." -Ayrton Senna