The short answer is “It’s just policy.”
It started out of Castro’s coming to power and taking over property that was owned by the US (or at least US companies). All except Guantanamo Bay. (“Go ahead–make my day!”)
Then there was that little incident at Bahia Cochinas where our invasion force basically took a rather sustained spanking. (I’ve heard that part of the reason for the defeat was some backroom skullduggery by Adlai Stevenson–don’t know if it’s true.)
And the noive of dat guy, allowing nukes to be parked only 90 miles from Key West–think of what that was going to do to tourism.
And to top it all off, he aligned himself with the Soviet Union–you know the bad guys.
Another major thorn in our side was the he and we (the US) always seemed to come down on opposite sides as to what dictator we wanted running various Third World countries (like El Salvador and Nicaragua). The guy that he wanted to be dictator was never the guy that we wanted to be dictator.
Well, his main sponsor has fallen apart, and the our dictator/his dictator wars in Central America are pretty much gone, so I join in the chorus of voices calling for an end to the embargo.
It comes down to two things (in my opinion): early in his term, he embarrassed us, and later he engaged in numerous proxy wars against us.
The first item is history, literally and figuratively, the second is also, just not quite so long.
So let’s do it.
I was in Key West just last month, and I would love to have taken a side trip to Havana.
Maybe next time.