Cuba could have had modern and progressive infrastructure, were she located in Europe. In this case in the post-worldwar colonial system of the USA Cuba would have had the status of ally, which mean to have fully integrated economy and equal social standards. But that form of satteliteship which was destined for Cuba and other Latin and South American states reflected highly unjust relations, as the US domination thrust on them the highly disbalanced skewed economical-social system, characterized with too obvious robbery of their societies in favour of american one. If to say idiomatically, their Manhatten was designed too small and their Harlem - too big and overwhelming to have sustainable balance and social approvement and tolerance. The leftist ideology was only the flag of their intention to change it by any way, as this of course could not be allowed by the US voluntarily. The US blockade of Cuba and not so direct systematical uprooting of any bilateral (and all other not-curcuited to US) ties between the countries of the region, the cultivation of political instability inside of them - that didn't allow them to merge in one big market for decades. The capacity of the local market and it's outer components - here's the answer to your question.