You shouldn’t have to… Any soldier worth their basic training should (if they don’t already know our rank system) assume that you’re a Company Sergeant Major.
You don’t have to… You’re not a Major. If someone confuses you with being one then there is no need to return their salute - a simple “Don’t salute me mate… I’m a Warrant Officer” usually does the trick.
I’m not sure why.
Does what it says on the tin
Doesn’t help that it’s harshly lit/over exposed.
I’d like to think the ‘20 yr old idiot WO’ on camp at an RAF station in the Sgt’s mess died with the introduction some years ago of the Adult SNCO career progression to WO. If they have made it far enough, passed the paperwork and have been highly thought of enough to earn the rank of WO in the RAFAC, then why not mirror the parent service?
Yeah, it did. Though because in some parts promotion is (or at least was) handed out almost automatically as a “well done” for being basically mediocre in current rank, we now have a collection of “30-40 year old idiot WOs” instead… 
Fair enough!
… You’ll see 
I can personally vouch for that 
Yours will be colour by numbers to match that youthful, cheeky chappie grin.