Imagine publishing a daily newspaper with exactly the same stories that you published the previous day. People would soon stop buying your newspaper.
Whilst not every website needs to say something different every day, if your website hasn’t been updated in 6 months, what use is it to your customers? They are more likely to distrust the published information for fear that it is out of date and turn to a competitor.
A website is a tool that can provide your customers with information at their convenience. If customers think that there might be something new since their last visit, they are more likely to come back to find out what it is.
The more often you can entice your customers to come back to your site, the more customer traffic you can generate, the more often you have the opportunity to sell to them.