Why is it worth doing cross-linking on a website? Quite a lot has been written about this on the Internet, I’ll add a few words of my own. I recently wrote about links  and there is an example in this post of linking. 

Why do relinking? First of all, for visitors to your resource, there is a semantic connection between the articles. So that the user does not immediately run away from the site, that is, to interest him in clicking on the link. There is a lot of debate about how the latter should open, in a new tab or not. It all depends on the situation, the external one is definitely in the new one, if the link is internal according to the situation. 

For search engines, linking is an additional improvement in the indexing of your resource. In simple terms, the more chaos there is in the sitemap, the more interesting you are to Google.

What does linking give:

Increases relevance; the link mass makes it clear to the search robot that the page meets a specific request.
Increases static weight, this indicator is important for SEO optimization. Together with other factors, it raises the site in search results.
Speeds up indexing. When a page is checked by a search algorithm and an unknown link is found, it is entered into the database.
Increases attendance and has a positive effect on behavioral factors. It is easier for the user to navigate the site. Perhaps he will come back to you again for useful information!