Search is the one channel where people are actively looking for what you sell. They have a problem, they are describing it in their own words, and they are ready to act. Being present at that moment costs nothing per click and compounds over time.
Good search work is mostly unglamorous: making sure your site can be crawled and understood, that each page answers one real question properly, and that the pages people find actually lead somewhere. It is an asset you own, unlike rented attention.
Ignore search and you become dependent on paid channels. The moment you stop spending, the enquiries stop with it, and your cost per customer is set by whoever is willing to bid the most that month.
It is also slow to recover. A site with broken structure, thin pages or a botched migration can take months to be re-evaluated, so the cost of neglect is not paid on the day you notice it. It is paid across the following year.