Why the Title Tag in Website is implemented for optimization?

Your page titles will show up in the SERPs, so make them concise and relevant.

Internal optimization refers to on-page and on-site activities. On-page activities include
keyword optimizations of <title> tags, description meta tags, page copy, and link
anchor text.

Concentrate on making easy, clear-cut, and logical interfaces with a focus on getting
to the right information quickly. Link anchor text should be of reasonable size and
should be similar to, or the same as, the destination page’s HTML title tag text (if it
exists).

TITLE element to identify the contents of a document. Since
users often consult documents out of context, authors should provide context-rich titles.
Thus, instead of a title such as “Introduction”, which doesn’t provide much contextual
background, authors should supply a title such as “Introduction to Medieval Bee-
Keeping” instead.
One of the most critical on-page factors, the <title> tag is not to be dismissed. Search
engines tend to use the <title> tag text as search results titles. All pages should have
unique page titles. All page titles should be crafted wisely, using the most important
keywords found in the page copy.