Why the push for background checks?

You hear more and more about this today.  After reading this post from the Ace of Spades blog, it appears that the government can block the purchase of a weapon on many, many grounds.  Hence, the background check.  They want to prevent more people from owning guns.  Here are the grounds for denying a purchase:

(g) It shall be unlawful for any person—
(1) who has been convicted in any court of, a crime punishable by imprisonment for a term exceeding one year;
(2) who is a fugitive from justice;
(3) who is an unlawful user of or addicted to any controlled substance (as defined in section 102 of the Controlled Substances Act (21 U.S.C. 802));
(4) who has been adjudicated as a mental defective or who has been committed to a mental institution;
(5) who, being an alien—
(A) is illegally or unlawfully in the United States; or
(B) except as provided in subsection (y)(2), has been admitted to the United States under a nonimmigrant visa (as that term is defined in section 101(a)(26) of the Immigration and Nationality Act (8 U.S.C. 1101 (a)(26)));
(6) who has been discharged from the Armed Forces under dishonorable conditions;
(7) who, having been a citizen of the United States, has renounced his citizenship;
(8) who is subject to a court order that—
(A) was issued after a hearing of which such person received actual notice, and at which such person had an opportunity to participate;
(B) restrains such person from harassing, stalking, or threatening an intimate partner of such person or child of such intimate partner or person, or engaging in other conduct that would place an intimate partner in reasonable fear of bodily injury to the partner or child; and
(C)
(i) includes a finding that such person represents a credible threat to the physical safety of such intimate partner or child; or
(ii) by its terms explicitly prohibits the use, attempted use, or threatened use of physical force against such intimate partner or child that would reasonably be expected to cause bodily injury; or
(9) who has been convicted in any court of a misdemeanor crime of domestic violence,


to ship or transport in interstate or foreign commerce, or possess in or affecting commerce, any firearm or ammunition; or to receive any firearm or ammunition which has been shipped or transported in interstate or foreign commerce.

Even Obama himself has violated this law, but nothing is done.  I think the point is clear.  YOU ARE NOT GOING TO BE ALLOWED TO OWN GUNS.

The $64K question is why the hell not?