What I know about carbon is that it is even lighter than titanium. Can’t say that it is the most durable material for a watch, but at least, it is as resistant to corrosion as ceramic and steel. People thinking of a carbon watch should understand that it still can be broken under extreme conditions, even though it is durable and resistant. So, everything is reduced to HOW you treat your watch. Also, the design aspects count a lot here. If making abstractions from resistance, carbon watches have a robust and powerful appeal. This is what makes them attractive to many sports lovers.
As for the watch manufacturers, they always use all means possible to increase the value of their products and carbon is not an exception. For any material, be it the most usual one, they will find resounding descriptions to make a strong marketing