when one of your inner pages constantly ranks on page 2 of google (spots 11 to 13) you will want to push it onto page 1 of google, where most of the traffic is. That's when you point a few quality backlinks (guest posts usually) at that particular page and give it 2-3 weeks AFTER the backlinks have been indexed by google to see if your inner page gets pushed onto google's page 1. If it does, cool! You've increased your traffic and (hopefully) revenue.
If it doesn't get pushed to page 1 of google then you either need to point few more backlinks to it and wait again, or give up because the competition is too high.
But generally, you will want to point most backlinks to the homepage to increase the authority (that bogus DA metric that everyone talks about) of your domain so you can increase its monetary value but, more importantly, increase the number of keywords that google will rank you for