The reson that exists is because of the fact that Cuba is a communist country, with no freedoms unlike mexico or the other countries you mentioned. so a person deported back to cuba (after floating 90 miles) will be executed by firing squad or jailed for treason.
That's right, Cuba's gonna kill or imprison for treason all returned deportees on sight ... that's why so many of them have been, right? Gee, those people who've tried to get to Florida from Cuba on multiple occasions must be really good, seeing as they avoided the firing squad.
Cuba's not wonderful, but it's a lot better off than many of its neighbors, most especially Haiti, regardless of government. If you don't see the irony in the fact that a Haitian and a Cuban both can float to Florida, but one will be returned and the other not based solely on policies stemming from an antique embargo, then you possess absolutely no sense of irony. How much safety do you think a Haitian faces upon return? Far less than the Cuban, I assure you. Booklet for food rations? Hell, the Haitians are lucky to get food at all, let alone a ration booklet. The US also deports people back to China with some frequency, yet China remains a despotic Communist country last time I checked; no trade embargo, either .... hmmm.
BTW, most Cubans today come to the US for exactly the same reasons that most other immigrants come to the US - jobs and money. I have no problem with people immigrating for economic reasons. I have every problem in the world with people who cloak their economic motivation in political talking points about freedom and democracy, when the truth is otherwise, then turn tail and wag their finger at other immigrants trying to gain entry for the exact same reasons. That's not irony, it's hypocritical.