These are some reasons why you should also consider using long-tail keywords:
The traffic of a higher quality and bigger conversion rates. Long-tail keywords are more specific. Compare “games” vs. “education games for kids.” The second query is more relevant to the searcher, so it can attract higher-quality traffic and has a greater conversion potential.
Long-tail keywords are less competitive and, therefore, cheaper. People often ignore such keywords, as they imply more work and advertising expertise.
More sustainable results. If you target only popular keywords, the chances are that a big player will come and outbid you, which will cause your impressions and revenue to drop immediately. With long-tail keywords, all traffic is distributed between multiple keywords, making the problem less pressing.