There is no such thing as a silly question, just silly answers
......and anyway, shouldn't it be
Howaaaaaay noo broon coo-man.....
On a serious note....the answer is obvious really, an atco needs to be understood at all times, a strong regional accent is not a good thing, and as such will put a potential controller in a very weak position when applying for a post. No voice training is given, because people who are hard to understand generally need to find another vocation.