It doesn't help your homepage's PR significantly. If your inner page links to your homepage, that link affects your homepage PR. So if you can increase the PR of your inner pages, you then have higher PR pages linking to your homepage. It does help with improving your rankings for your inner pages.
it does help the bots get to your inner pages.. you must have external links to those pages if you want PR
Linking to your inner pages helps the rank of those pages just like linking to your index page helps the rank of your index page. A page to a bot is just a page...
If you get a link from an external site to an internal page on your site and then your internal page links to your index page it will increase the PR of the index page. If you link from your index page to an internal page then you're passing PR to the internal page. If the internal page links back to your index page then you're passing some of that PR back to the index page. What you really want to do for your own internal link structure is have your home page link to the most important landing pages on your site. Then have the landing pages link to the next most important pages and so on. Then make sure each level links back to the level above it and to the home page. This will distribute the PR most heavily on the pages you want showing up high in the SERPs.
So this means whenever we wrote new post we should keep updating inner page link in sidebar option too .So the bots can easily get into our inner pages .
It is a good method for good site linking structure. If you could notice, sitemap of most sites have good PR.