It is like not offering ketchup for French fries.
That actually happened to me at Cork&Slice in Cedarhurst, ruined an otherwise great experience (food, ambiance, was great, service OTOH was sorely lacking).
They actually made me feel stupid for asking for Ketchup, and when I realized they weren't going to give me any (they were uppity about it, since they are a fancy "Italian" eatery), I asked them if they could give me something else to dip their fries in, they once again looked at me like I was nuts and told me that this is how the fries come.