Wp_link_pages problem

I’m doing my first own theme and when I tried to add it to the theme directory, scanning failed because wp_link_pages couldn’t be found and it was required. After checking the Codex page I added it in Loop as said but it doesn’t seem to do anything. Any text isn’t showing up either in actual page or in source code. Is it okay or do I have to fix something? From what I understood from Codex, it’s supposed to do something with pagination but my pagination was already working even without it so I don’t really see why it is required…