Do they? I don't think anybody cares about fettuccine Alfredo in Italy, it's not something you will find on restaurant menus or that people cook at home.

In 40 years I've never had it, and I'm a Rome citizen.

I'm quite confident most Italians don't even know what's in the recipe besides maybe hearing there's butter.

I did try a month ago to go to the original Alfredo restaurant near via del corso, but the queue and prices (28€ for the pasta alone is crazy) made me go to the restaurant literally on the other side of the street. It was quite clearly a tourist trap.