Vegetarians buy those burgers, other people don't. People simply don't care about other reasons, they care if the product tastes good and is cheaper, they'll also consider health (i.e. lower fat/chemicals/processing/etc). That's it.
And this cheese has an even harder sell: There are even fewer vegans than there are vegetarians.
Their only hope is for this cheese to be cheaper than cow cheese, and based on their website and lack of retail sales I doubt that it is.