There is a wealth of evidence to suggest that while ideologues such as Thomas Paine were certainly avid supporters of the principles of the Declaration (and Andrew Galambos claimed that he could prove that the Declaration was actually authored - at least primarily - by Paine), other of the "founding fathers" had other agendas.  One item that I have heard frequently is that the British Empire had already essentially outlawed slavery by 1776, in a phased out progression.  Thus, slave owners in the 13 colonies were happy to have their own quiet ambitions furthered, regardless of some silly claptrap about inalienable rights.

Additionally, many Tories had their property seized by the revolutionaries, regardless of whether they actively participated in any anti-revolutionary acts, and many were forced to flee to Canada or other parts of the Empire.  Getting rich quick from seizing some one else's property - especially that of a hated minority - has long trumped notions of human rights.

More importantly, however, it has been claimed that at the end of the revolution, and, perhaps, one of the driving forces behind it from the start, was the repudiation of enormous debts to British banks and other investors, debts that had financed the colonization from the beginning.  I would suggest that possibly yet another economic incentive was the freeing up of patents.  I recall that there was a huge clampdown on use of patented industrial technology by the British mercantilists against colonists.  The revolution had the impact of putting an enormous amount of intellectual property developed in Britain into the U.S. public domain.  (~"The property is there.  Who cares who created it?"  - anyone recall the exact quote from AS?)

The gist of the missing 13th Amendment debate is roughly that the British banks had schemed from the end of the revolution to recover the stolen debt assets, and had managed to slip in various measures via their U.S. lobbyists that opened the door to such claims.  Among these measures was a weakening of constitutional provisions against a U.S. gentry, as in the "Esquire" that attorneys often append to their names.  Note that these measures were successful enough that judges throughout the U.S. today - as far as I know - are required to be members of the Bar, which is a private organization which sets its own rules and limits membership to those who tow its ideological line via Bar exams.  Talk about fascism.

The missing 13th, which allegedly overturned the alleged behind the scenes British plotting,  was about to be recognized in Washington, apparently, as it appears that the number of states required for ratification had been achieved.  Some researchers speculate that this was the primary reason for the War of 1812 and especially the successful march on Washington and its burning by the British army, which destroyed all the Washington based records of the 13th's passage. 

My point?  The U.S. from the start leaned strongly in the direction of mercantilism, with special tariff and import duty privileges (literally "private laws") fueling the creation of a new class of gentry.  Of course, in any such scheme there are victims.  Ironically, the primary victims of the Northern mercantilists were the very Southern cotton growers who had benefitted from getting out from under the Empire and keeping their slaves, but who were now being destroyed economically by the tariff structure, which forced them to sell at drastically reduced rate to the Northern textile interests, instead of the European markets, who were willing to pay a much higher price. 

Thus we fought one of the bloodiest wars in history to protect our own landed gentry from free market competition.  The Declaration, meanwhile, is a pretty piece of paper.