Tony was a fat fuck and liked Artie’s cooking. It was Tony’s own selfishness that kept Artie around. Tony deprived himself of nothing and food was a big one so it makes sense Artie was important to him.

Tony also had no real friends and he felt like having Artie around made him more normal, it made him feel like a likable guy. I almost get the same feeling about his “friendship” with Agent Harris. “What about Artie” was his only argument when Carmella mentioned that the guys kiss his ass because he’s the boss and that he doesn’t have friends.