Since when are more choices a bad thing? Only a blind Apple fanboy would ever think that LOL Who cares how many phones a company sells unless you have stock in it. If you have an Accord, are you sitting there counting how many Honda sells and blasting people for buying a Camry?
As someone said earlier, this is different because people expect continuous support, updates, and new/great software built specifically for their devices. When a company has a large number of different devices in the same category, and is continuously pushing the new one on you, they lose the incentive to provide these services to the customer.
On the contrary, doing so would actually
lose them money, because they only make money on the initial sale, and need people to buy new devices in order to make more money.
Considering this, the car comparison is not valid.
For a comparison, consider the video game console market. If you own the Xbox360, you want everyone to buy that instead of the PS3. That way, more software is made specifically for your console, instead of being ported over, resulting in much better software and a much better experience for you, the consumer.
Now imagine if there were 100 different Xbox consoles, new ones were coming out every few months, all with different supported resolutions, different hardware buttons, different aspect ratios, different pixel densities, different graphics cards, different CPUs, different number of CPUs, different software running in the background, different OS versions, different audio subsystems...etc.
This is the complete opposite of what you would want as an Xbox owner, as it would pretty much guarantee that no software would be made for your specific console in mind.