Nowadays there is as many graphic design jobs available online as amount of designers seeking for them.

In result the computer graphic market is quite competitive, that why as a good freelance graphic designer you need to be the one who stands out of the crowd to get noticed.

Some artists specialize in particular categories of digital arts. While the one is much into commercial design such as: advertising spots or web design the other one is more creative in illustration.

It's hard to be multi talented in all aspects of digital arts, that's why choosing speciality and working towards it is what it's all about.
If you want to be a good designer who receive a lot of commission work, improve your skills in particular CG area. Once you master it you can always try to learn something new if you have some extra time.
However while browsing portfolios it's not hard to notice that usually different artists represent
their own particular style worked out and mastered through the years and that makes their work outstanding and unique in front of the other designers.

So the point is that the artist who tries to be good at every possible computer graphic area usually ends up on being average on it as it's hard to spread the skills and time doing quality projects from "different shelf" at the same time.
Unless the one is that talented:)

Creating the own style in particular CG area you mostly enjoy and improving your skills in it will bring you customers hungry for your projects and make your work noticable as there is high demand on every single kind of digital arts.