If google is not caching your website, it means you need to update your website. If you are update your website frequently and still your site is not being cached, it means you need to check whether your “If modified since” header is on or not. Because this header tell crawler about update happen on your websites.
Second reason may be uselessness of your updates. If crawler think that new update is insufficient to its data base, your website will not be cached.
Third reason is: No one is searching your website. No one come on your website and does not navigate.
Fourth reason is: You have not patience. Keep it and wait. Meanwhile you can do offpage activities to welcome crawler from various other different ways. It really work.