Why use long-tail keywords if they have low search volumes? Because search volume is not the decisive factor in keyword quality.
Other factors, such as intent and competition, should be considered when doing keyword research.
Long-tail keywords have less competition
Short-tail keywords are incredibly competitive (expensive) — everyone wants a piece of high traffic SERPs. But because they are so competitive, only the highest authority websites get to rank on page one.
Long-tail keywords relate to a niche of products and services, where it’s easier to compete.
Long-tail keywords have higher conversion rates
Users who search for more specific terms are further in their buying cycle than searchers who use short-tail queries. Long-tail keywords have 2.5 times the conversion rate of short-tail keywords.