When a person hits a page they chose from Google's search results, they decide in about 8 - 10 seconds if they're staying there. If the page doesn't speak to them immediately about what they want, they leave. They probably won't even read a full sentence of the page copy.
The act of their leaving is measured by a metric called the "bounce rate". Lets aim to get the bounce rates down for your site - because bounce rates mean you will be losing money.
When people search, they get thousands of pages of results. You might be top, but if you're not chosen for a view you may as well be bottom. At least your bounce rates will be low!
If people want item A, and you have item B, then a sale is not likely to happen. You might be chuffed with being on page one for item B, but who cares?
You may well have item B, but if you are calling it item C then nobody will come to you to buy it. This isn't straightforward because it may not strictly be about words. Early on in my own career, I had a job optimising for a new grass seed - it didn't have any search phrase because nobody even knew it existed. How would I optimise for this product?
The answer was simple - optimise for a keyphrase that attracted people who would buy the product, not for the product itself. Within one week the client was selling this product that had no keywords that directly described it and that was 8 or 9 years ago at the time of writing this.