Cheesesteaks, like most Roadfood, is subject to regional variations.
In the Lehigh Valley, where I live the default version of the cheesesteak comes with sauce.
My wife likes this version, which means that, when we are in Philly she has to order a pizza steak.
I, on the other hand prefer my chesesteak without sauce but with ketchup (and Mushrooms).
Locally, this means I have to tell the server "CHEESESTEAK, HOLD THE SAUCE". When I then proceed to add ketchup, I sometimes get some quizical looks-like why are you adding back in something similar to what you told us to withold.
The answer, of course, is that ketchup is quite different than marinara sauce. Also, if I add the ketchup I can control the quantity (I typically put on far less ketchup than the amount of sauce that the kitchen would normally add).