Its all about money and corruption.
Haitians don't wield any significant political power in the US.
Meanwhile, the USA is spending hundreds of millions of our tax dollars annually to overthrow the Cuban system of government, which has created universal health care and universal education systems according to the will of the people, that Haitians (and people from all over the Americas) would give their 'left one' to have access to.
Why so much against Cuba and so little for Haiti?
graph from www.opensecrets.org
The US political parties milk the monied Cuban-America PACs and the pro trade agri PACs for all they can by maintaining the standoff between the two countries. One way to maintain the Miamicuban "exiles" financial support for political campaigns is to pour millions of taxpayer dollars into the pockets of hundreds of "free Cuba" exile run foundations.
Cubans that arrive in the US illegally are granted a host of immigration perks by the US Cuban Adjustment Act.
Haitians that arrive in the US illegally are incarcerated until their deportation.
Haitians do arrive in Cuba on overloaded boats, but Cuba doesn't incarcerate them prior to their immigration hearing like the USA does. In Cuba, Haitian refugees have more immigration rights than they do in the US. There is a significant Haitian refugee community in Cuba.
A common refrain heard in Miami's Haitian community when discussing Caribbean politics (although it is whispered because of fear of reprisal from Miami's radical Cuban "exile" elements) is "in Haiti, we would welcome ten Castro's in place of one Aristide".