Yours might be. You already have a developed skillset.
But, someone asking that question should probably not be doing it. Hosting is cheap. Learning system administration is extremely time intensive, not to mention keeping up with patches, exploits, etc.
Sure, the average host out there might not be that secure or reliable, either. If someone were really bent on hosting themselves, they can go with an unmanaged dedicated server at a good datacenter.
Most people who are just running a few websites don’t need or want the headaches associated with server adminstration. If you want to do it for fun or knowledge, go ahead. If you want to do it to save a few dollars in hosting costs, you’ll probably eventually wish that you hadn’t. You’ll find yourself buried in a sea of information that has little to do with operating a website, and everything to do with keeping a server secure. Even then, you won’t beat the people who really want in.