I think the problem is mainly that they don't have control over what you do with them, and not necessarly with the name, as they are commercial and competitive products.
Let's say you take a Glock 17 and a Beretta 92F in your game, which are both pretty similar handguns. But, for the Glock 17, you put it as a very very lowsy gun, with no accuracy and that it always jams and doesn't deliver much damage. But, for the Beretta 92F, you put it as great, accurate and lethal.
Same thing applies to cars, if you put a Dodge Viper 2006 and put it slow as a snail and put it a Hyundai Pony 1985 that's faster than a rocket, I don't think Dodge will like that if your game is very popular.
Let's say you take a Glock 17 and a Beretta 92F in your game, which are both pretty similar handguns. But, for the Glock 17, you put it as a very very lowsy gun, with no accuracy and that it always jams and doesn't deliver much damage. But, for the Beretta 92F, you put it as great, accurate and lethal.
Same thing applies to cars, if you put a Dodge Viper 2006 and put it slow as a snail and put it a Hyundai Pony 1985 that's faster than a rocket, I don't think Dodge will like that if your game is very popular.