Making your own website is a lot like anything else. Some people have the time to learn the very basics and an eye for design and will be able to make a presentable site. There will be a lot of things they won’t know how to do and they will have to rely on templates provided by the web hosting company and will have to settle for what they can do.
It is not easy to make a professional website. Learning to make a professional website is something you go to school for and spend thousands of dollars in software. You learn HTML code and then CSS code and then all the other codes and design elements you need to know. Even then there are still limitations, more plug-ins and software to buy, or Web Programmers to consult for special programming needs. The web is also constantly evolving and a web professional has to keep up.
Some businesses will need sites that can scale to mobile devices and I have yet to see a DIY site to handle these needs. If your business caters to people on the go, chances are they will need mobile device capability.