It takes a lot of work to remake a car, these models will usually be used in media .
So basically BMW is reducing the media coverage of their range by doing this and potentially alienating potential marketers of the product.
Some buyers of this 3d model type would generally be needing it to do "crash" simulations to sub into indie movies.
Others might just add it into a first person shooter to have a larger selection of cars to hide behind and shoot at.
A few might even try to make a crappy 3d print out of it.
I dare say that most of the 3d models for sale would be useless in the hands of other car making companies.
So in closing it looks like there will be less BMW's as a direct result of them "protecting their product".