Someone just asked this lol - Because they generally bring in qualified leads cheaper and more competently than traditional methods. And because you would lose significantly more resources through time in research, money in failed budgets, and opportunity costs from lack of knowledge, by doing it yourself than you would to pay the fees of an experienced agency. My job is effectively to make other people money. If I didn't make them significantly more than what they paid me then I failed at my job. Additional response for the comments here - I don't personally believe in hiring people or freelancers rather than agencies. Let the agency hire people and freelancers, but it is better to be deal with agencies that have a vested interest in your results. Freelancers or people that do things on the side have upsides for doing good work, but no downsides for doing bad work because they don't have enough notoriety or branding to be punished when something goes wrong. This means that it often enters into a conflicting interest where it is not worth it for the freelancer to do the finer details or maintenance that comes from agencies. Unless you are hiring them for several projects and they have vested interest in your performance freelancers can be very dangerous. I see so so so many websites done by freelancers that are completely broken. This happens with agencies too sure, but so much more often with freelancers that don't have as much experience, don't have outlined processes, or are trying harder to hit their monthly quotas to pay their bills.