As a rule the web site do not freeze, it develops as your business does. You do not want to bother technical things as what to do with a strange technical mail from hosting company, how to add a new link to site, new photo or page. Then you need a person who can professionally take care of your site.
The site should be regularly checked. If needed, security updates should be installed. Otherwise you are at risk to be hacked. The site can be broken, can be marked as dangeros in search engines or even banned. You can fall out of online business for weeks.
The main goal of web site support is freeing you of headache of technical problems. The site just works.