So what if there were 100 or more small scale experiments in 50 different countries, in similar conditions. I won't be playing with the money of the entire nation|state|county|city to possibly lose it and not get elected again!
I want vaccines to be tested on 30% of the population to see if it works.
We should be putting this prototype hardware in the hands of 40% of the population to see if there are any side effects before deciding whether to legalise it.
We will do a double blind test on 50% of the population with these new safety regulations to see if there's an impact on incidences. The study would be invalid otherwise.
Models and small scale experiments are for wimps. I, the ruler of the democratic country, declare an experiment shall be run at national scale! The economy of region X with will not be comparable to that of the rest of 90% of country!