Websites can be built to function unattended for decades. Much like a book — as long as the content is right, it needs no changes.
If a website — like this one — uses constant text and images every time it is accessed, it can do its job for decades. Like a book on the shelf. The technology for this has been almost the same since the beginning of the web in 1992, i.e. what follows these basic rules today will still work in a small eternity.
The much-cited fast-moving nature comes from the latest fashion trends in design and tools. These become outdated and need attention several times a year. Similar to the way clothing fashion, for example, 'reinvents itself' every year, yet a buttonhole is always a buttonhole and needle and thread always remain the same.
The reasons may be similar here and there, because otherwise clothing manufacturers would make lesser sales as well as advertising agencies and web designers. And the "smarter" something is, the quicker it becomes electronic waste — but is great to advertise for today. Especially if the customer doesn't see how little is actually enough to achieve the desired result.
As an association, private or self-employed person or small company, it is usually useful to have your own shop window on the internet with a short introduction and contact. That's often enough, by far, and doesn't tend to outdate.
The same reasons favour doing something yourself on the digital as in analogue life: