Many companies take on their own marketing of their business. It may be that they employ internal marketing staff or often they just use other members of staff who are not trained in marketing to implement strategies.
If you are employing staff to work on your marketing and they have experience and or qualifications in this area then that may work well, but if you are utilising other members of staff that do not have the qualifications or experience then you are not only taking them away from the other work they have to do but also risking getting the marketing wrong. As a company, you can end up investing money in to the wrong marketing avenues meaning you get little or no return on your money that you put in to it. That’s where a marketing consultant can help. Even if you do not want to outsource your marketing, they may be able to advise you on what you should be doing and even offer training to the staff that are going to be implementing the marketing.