Short and sweet- your company must interact with people to sell them.
Why should you advertise? Because nobody but your friends and family, if anyone, gets a phone call or a text message telling them, “Hey, so and so is in business, come buy.”
If you rely on word of mouth in the age of technology, you are losing money. Even if you think you are successful, it may be because you are not fully aware of your true potential, and you have not seen what your real success can be.
Advertising is a pool all can swim in. There is an approach for almost every budget, and the key is to advertise to the right audience somehow.