In VPS servers your website is hosted in a container. It means although you are sharing the server with other websites, you have your own isolation and privacy that a business seeks. You cannot move out of the container and disturb the other websites and they in turn cannot meddle in your environment. VPS is highly reliable. Unlike in shared hosting, your website performance will not be affected even at times when neighboring websites pull more resources.
Similarly, if you draw more resources to manage sudden spurt in traffic, the other websites will continue to perform in their normal way without the fear of server crashing. You can also easily backup your data and other applications to server your customers better. Likewise, even if one of the components fail it will not affect the websites as they continue to draw resources from the other active components on the server.