I guess it depends on the marque/s that you sell... If it is something a little harder to find or exotic, customers are going to enquire from further afield and may want to purchase over the phone.
Years back I once bought an Audi from Belfast 'unseen' and flew over to collect it. But the dealer gave me lots of confidence in the condition and was very honest on the phone about the very minor scratches. Its all about building confidence through transparency and trust. But ultimately I agree, your customers should come to you and as long as it is 'as described' or the true condition is shown in photos and videos, then you have nothing to worry about!