It's one of the objections I will run into every once in awhile. And it may be true.
Do not fool yourself into thinking that you don't need to be actively marketing.
I'll take a second here and explain the difference.
When most people think of advertising, they think of paid advertisements. This includes direct mail, newspaper ads, magazine ads, billboard ads, television ads, radio ads, etc.
(Notice the word ad, fits nicely behind each of those options.)
Advertising is a part of your marketing.
Marketing is how you and your company presents itself to your market.
This includes everything from your business cards, how clean your windows are, how your phone is answered, the way you treat problems, the way you thank your customers, etc.
If you have a waiting list of customers and clients then maybe you don't need a paid ad campaign.
But you better be sure everything else is as remarkable as possible.