maybe it's because the sign outside only says "Restaurant", and so it looks like it could be any corner greasy spoon. they don't actually say where the restaurant is, so, since it looks like a generic diner, we are left to assume it is somewhere in the neighborhood. you must remember that most people watching the show do not even live in NY, nevertheless across the street from the joint.
Where Does Elaine Live?
S05E17 The WifeliveMar 20, 1994, 12:43 AM ET3 days later2 posts by 2 posters
🧠 Theory
Fans debate whether the exterior diner sign clearly identifies the restaurant as Monk's, with disagreement over visibility of the name on the glass door.
2 posts
Actually, they *do* refer to the "Restaurant" (not gratuitous quotation marks, mind you, as I am quoting from the sign) as Monk's, and once in a while you can see the name painted on the glass door when they go in or out.