It sounds like you are a single developer working on your own site. If this is the case, it's not necessary at all, but it is still a good idea for you to learn as a part of your professional experience.
Automated building of projects becomes more necessary as the number of developers working on a project increase. It is very easy for two developers to write incompatible code which will break when it is combined (imagine I'm calling a function foo(int x), and you change the signature to be foo(int x, int y): when we combine our code bases, the code will break.
These types of errors increase in complexity and hassle with the amount of time between integration builds. By setting up nightly builds, or even builds that occur every check-in, these problems are greatly reduced. This practice is pretty much industry standard across projects with multiple developers.
So now, to answer your question: this is a skill that will span across projects and companies. You should learn it to broaden your knowledge and skills as a developer, and to add an important line on your resume.