Coffee mug here. I do it for portion control otherwise I'll eat way too much ice cream. A bowl is like 3 scoops and thats far too much for my diet. When I use my coffee mug I only have like a lil over 1 scoop and its perfect that way.
If I'm being a glutinous cretin and go for a banana split sundae then I'll put that in a bowl.
I haven't had a cone since I was a kid. Really don't have any interest in eating ice cream that has the possibility of dripping all over my hands.
If I'm buying ice cream I want to eat ice cream, not ice cream + cheapass cone(good quality cones are the exception). Feels like most places give you more ice cream for your buck if you order cup, so that.