When updating a website usually only the front-end is being redesigned

If when updating the website not only a new design is needed but also a change in the database structure and a new content management system it would be cheeper and easier just to make anew website.

As much as we don’t like it every thing gets older.
Websites are no exception to that.
When expanding, changing your business model or any other circumstances, increase the productivity, use of new informational technologies, websites need to be updated. When new technologies emerge, there is a wish to use them and improve with them. The most common the design update.
But sooner or later it becomes old, it is no longer attractive, no longer meets the realities of fashion and so on.
Often in addition to partial or full design update there is a a need to change and upgrade the structure and and arrangement of information in the website.
In some cases the content management system is updated not the design.
Because the older systems does not satisfy growing need.