My guess is that on the other side of the pond, a member of the armed forces would probably go to the head of the queue.
It does make me feel ashamed when people I've worked with try to pull this stunt, thinking they deserve better treatment or a reduction in price from a family owned small business. Despite the fact they've stayed in the UK working behind a desk.
There's plenty of other occupations who contribute just as much to society, who we could not do without. Yet they don't walk around in uniform just to get special treatment.
I never ask for discount because I don't think I've done anything special. I'd feel embarrassed to cash-in on the bravery of others.