No, not all, there are some categories where advertising is much less relevant. If a category only has a small number of customers, then it does not need advertising’s reach to get to those customers. For example, if you are selling cement to the building trade in the UK, then it is probably the case that there are only a few dozen people who buy cement for all the building contractors. You don’t need advertising to reach them, you can probably send them all an email or just ring them up!
That said, the vast majority of small businesses are not in categories like this and do need to address a large number of potential customers.