I ordered mine debadged. Why?
1) I think it looks much better.
2) Easier to detail.
3) What is the point in proclaiming exactly what model it is to everyone? I bought the car for myself, I don't care what others think.
...and to address the (extremely silly) original question: Mine is an F31 328. Which means it IS the top of the line model (unless you count the 330d). So if anything my reason would be the opposite: I don't mind at all if my neighbors think it's a "lesser" model (320i, 316d etc.). It's already "shouty" enough as it is.
