Most big businesses do in house SEO. Some do some in house and outsource specific tasks (for example the in house staff may create and manage the editorial calendar and outsource writing).
To me the most important question is can small business SEO succeed in house?
Small business SEO is an interesting topic due to the economics of SEO.
Long gone are the days when inexpensive technical tricks was sufficient to rank your website. Now it takes content. Good content and a steady stream of fresh content.
That doesn’t come cheap.
Most small businesses can not afford to outsource the generation of a steady steam of quality content. Yet the standard story of how it’s best left to the experts indicates they can not do it successfully in house.
The problem with that narrative is it’s false.
You have to pay for your SEO results, but a relative inexpensive employee (as compared to an expensive SEO consultant) do it for you, provided they’re taught how and coached in their efforts.
The next problem is most of the SEO training and coaching available is pretty crappy and people tend to need more than just training, they need coaching. They need someone to periodically review what they’re doing and provide course corrections.
However it can be done. Anyone can learn how do to effective SEO, but to be effective you’ve got to do the work, not JUST know how.SEO Needs Link Building