Websites rarely fail all at once. They fail quietly: a form stops sending emails, a security update gets skipped, a backup that nobody checked turns out to be empty. Each problem is small on its own, and each one goes unnoticed until a customer tells you something is wrong, or worse, doesn't tell you and goes to a competitor.
The most common thing we find when we take over a site is a contact form that has been broken for weeks without anyone knowing. Every one of those weeks was lost inquiries. Regular maintenance catches these problems early, when they're cheap and quick to fix, instead of after they've already cost you customers.
