using links on your site to your same site

I see this a lot, is there any point to this?

Like say someone has a domain:

domain.com

And say there is a page on that site:

domain.com/keyword-1

So then on a different page on his site, he'll be like "blah blah blah, learn about keyword 1" and it's a link to that page. But obviously there is already a link to that page in his navigation menu, so it's like he's trying to get some extra linkjuice for it, but when it comes from the same domain, do you still get any SEO benefit from doing that?

every link helps, even if it's an internal link. not to mention it helps people navigate from page to page, even if it is on the nav bar.

Google will register the first link. You can nofollow the link and do follow the keyword link if the menu link is not a keyword. And yes you will get some benefit from internal linking keywords to corresponding pages. That's part of onpage SEO