Some businesses are dependent on traffic generated purely from advertising. First you have to ask, do you have repeat customers or are your customers predominately new customers? If you are a plumber, your business may have some repeat business but you may find that a lot of the business is new customers who are looking for someone to come out and repair their bathroom. Some plumbers may only want commercial customers therefore they may or may not advertise to the public. If you are looking for consumers, then how will the consumer find you if you do not advertise?
Some businesses such as accountants, lawyers, financial planners get a lot of their business by referrals. The cost of advertising may or may not be covered from work generated by new clients generated from advertising. Sometimes you need to spend a lot to get in the front pages of for example yellow pages. If you are a plumber with an ad on page 10 of the plumbers, chances are no one will see your ad. You become frustrated and you reduce the size of your ad and now you are on page 15 of the plumbers. You get even less phone calls. Does it pay to get on page 1, not if you cannot afford the costs? If this is your only way that you have been marketing in the past, then maybe it is time to change how you do your marketing. If you need to let the public know who you are and your advertising campaign is not working, you need to find another method of advertising.
If you are reliant on new traffic for your business in goods times or in bad, you will always need to advertise, you just need to perfect, what type of advertising works best for you. If you do not advertise and no one can find you, you will not have much of a business when you stop advertising.