I ask because my Dad dropped in on me at work, a public facing role where we see a wide cross section of people.
Dad didn't say who he was, just gave his name which is different to mine. My colleague came to tell me "there's a very respectable looking gent here to see you" 
My parents are proper old fashioned English eccentrics. Slightly wild hair, mum never wears make up, clothes from M&S or the supermarket, always chosen for comfort and practicality rather than style.
They're always clean, but not much more effort than that goes into their appearance and yet they do both manage to present as "respectable". Why is that?