Yes. Anyone can learn SEO, but it requires a lot of knowledge (programming, writing, data analysis) that few business owners have the time or desire to acquire. You should also ask yourself if the time spent learning all these skills would not be better invested in doing what you are good at: managing your business
In other words, you can do your own mobile SEO but you are probably better off relying on a mobile SEO agency that knows the discipline like the back of their hand.