There are several reasons to use semantic tags opposed to div tags, the main one being that it makes your code more readable and maintainable as each block of code has a descriptive label for what it is/where it should be displayed
The use of semantic tags also helps with search engine optimisation, as they allow the web crawler to rank sections of text based on their importance
Semantic html also benefits screen reader users, as screen readers use semantic tags in order to better convey the information contained on the page to the user