I don't drink so I never got a DWI or DUI, but I did have police officer that I know tell me he was going to issue me a DWS (driving while smoking). Told me I did not have full control of the vehicle while trying to drive and light my pipe at the same time.
You are correct, it is amazing what is exceptable and what is not. Someday it will be against the law to pass wind in public.