If all the back links of your website are pointing to your home page and none of them points to internal pages of a website then your website optimization campaign is not fully utilized.You may get good rank for home page keyword,but won't get good results for internal pages. The net result would be that you will get business for your home page only and not for internal pages. It is harder to bring traffic towards home page of a website,but more harder to bring traffic to internal pages of website. One of the easiest way of bringing direct traffic to internal pages of website is deep link directories submission. Main Purpose of SEO is to bring business for websites through website. It has been found that most of the time competition is tough on home page primary keywords and it takes time for website to rank well meanwhile competition on deep pages of website is low and takes less time to rank, hence if we put our 30 -40 % of effort in deep page promotion of website, chances of selling product or service through website becomes faster as well as easier that's why it is really important to promote deep pages of website and that could be done through deep link directory submission.