Why doesn't google show all of the links to my site?

Google has always shown only a sample of the links coming into your site. These links are updated in the search results every 3 - 6 weeks. Even though google only shows a small sample, this does not mean that google doesn't count the other backlinks when displaying search results. Google updates its search result pages for standard searches continuously, and these search results take into account all links that google has found.

Could you please more clarify... you mean to say that as google shows first 1000 results in SERPs..in the same way it shows some of the backlinks.. but for some sites it shows 20 and for some 100...what is the basis for displaying the backlinks
*** to view backlinks, we use:
link:www.abc.com

but i think we must use
abc.com -site:www.abc.com

Please advice.............