I didn't get my licence until my mid twenties, but I couldn't imagine life without my car now. I would sooner drive to town than get the train (and whinge about parking costs - one day I'll learn). That being said, most of my clients drive to me as I have never really had city centre accomodation; I've never liked the pricing, and I've traditionally lived a short 10 min drive away from the centre with free parking on my street.
Some clients take public transport. It doesn't really bother me how you get to me, just don't be a nuisance about it. I had a relative who was a driver but post stroke lost his licence because of how it affected him; there's plenty of people who can't drive for medical reasons, so I don't judge. Plus, cars can be incredibly expensive - car tax is going to go up, petrol costs are a fair boot in the balls when you fill up, and I'm lucky that my insurance is only a few hundred a year because I have a clean licence. I've jinxed myself now, but add points or a collision onto that, your insurance will start to creep up. It probably costs me about ?350 a month to run my car, if I include putting aside money in case something went wrong with it (my car is on finance).
So a client without a car potentially has more disposable income...? Swings and roundabouts really, but its a matter of perspective.