From everything I've read that has incidental talk of the tire naming, (and granted it is not much) it's not the manufacturers that invented the naming convention. In general it was the cyclist's in that respective genre of cycling. Salesman for tire manufacturers picked up on that convention and just used it to advertise to that particular segment in the common jargon of that segment.

I don't really have an issue with that, but what I do fault the manufacturers for is that some don't plainly list the ISO size of the tires, tubes or rims.