Kinda weird but it seems IMO that some shows that had cool cars didn't have a huge following and didn't go into a lot of seasons. Drive, Viper, Fastlane (Multiple cool cars!), Cobra (Shelby Cobra kit car). Maybe just poor plot lines?
Although Miami Vice lasted a bit, but it may have been the Don Johnson effect. Knight Rider did well too. Starksky and Hutch was cool but you didn't see the Torino all that much.