Say you had a VW Microbus, and the insides of the windows are permanently fogged with antifreeze from a leaky heater core. You lend your friend Eddie the Microbus for a few days, but before he picks it up you write "frist psot" on the front passenger window. After a day of driving it, Eddie loans it to his pal Joe to move a couch, but before he gives it up he writes "hot grits" on the back window. Joe adds "STFU noob" to the windshield, but before he has a chance to move the couch, his grandma needs to borrow the Microbus to get to a bingo tournament. This goes on and on for years. Eventually you get your car back, with every window covered in messages.
Now imagine there are hundreds of thousands of VW Microbuses in your pants. This is what's happening in Cuba.