Because Google faster forme yahoo and bing and google 75% result related to users.

Title tag show top of the browser and describe all about page in short.

Title Tags are Important for SEO. Browser. Title tags often show up in both the top of a browser's chrome and in tabs. Search Engine Results Pages. When you use keywords in the title tag, search engines will highlight them in the search results if a user has performed a query including those keywords.

yes tittle tag is very important factor of on-page technique because if you put tittle tag then google understand what is this article , and known as relevant.