The long tail is where most businesses make their money. Someone searching "seo agency" may be a student, a competitor or a buyer; someone searching "seo agency for shopify stores in lyon" has already qualified themselves. Aggregated across thousands of variants, this specific demand usually exceeds the head term it derives from, and it is far cheaper to win.
The practical mistake is building one page per long-tail phrase. Search engines understand variants, so a single well-structured page routinely ranks for hundreds of them. Build the page around the intent, cover the sub-questions honestly, and let the tail accumulate — a strategy that ages far better than a folder of near-duplicate pages.