A car manufacturer at least needs to invest in the materials and the production costs of each car they push on the market. With software, once you have finished all the data for a single copy of your product, it's a simple matter of making copies and selling them. Of corse there are expenses for printing CDs or DVDs but those are nothing like the costs of producing cars. And nowadays you could ignore physical distribution entirely and go for online distribution, which is even cheaper.

The point is that while a car is a physical object, software is just data. And producing a copy of a piece of data is ridiculously easy and cheap.