I will assume that's because they cannot get a visa and most definitively not for USA. Usually embassies/consulates know that Cubans are prone to stay illegally in their countries, therefore it is not that easy to get a visa just to visit a country as a tourist, you have to prove big time that you will return to Cuba (like employment, family to take care here, properties etc etc) , but even then, people that meet all those requirements and do get a visitor visa to other countries they will remain in those countries and not return to Cuba. On another note I can see now more people trying to get to USA as soon as they can since all the modifications to laws that could/will come with the new diplomatic relationships established by Cuban and American governments, which can translate that eventually USA can abolish the Cuban Adjustment Act which allows the USA government to grant political asylum easily to Cubans since they know they will be covered eventually by the Cuban Adjustment Act. But if that get removed then Cubans will be treated by the same rules as any other illegal immigrant trying to seek refugee in the USA.
Thanks again for the explanation. Very detailed.
Good luck with the rest of the process
Not that what I just explained justify what people do, but that's my assumption of why they do it apart from some other economical/political reasons they might have.