I've always been a big proponent of keeping a website up to date. It's important for the health of your site, your web server, to prevent hacking, and to the marketability of your site.
If you have a WordPress website, keeping the plugins and themes up to date are critical to preventing a potential hack.
Check out this podcast by SiteGround for more important tips!
https://geek2englishpodcast.com/routine-website-maintenance-and-why-its-important/