You can execute a vastly cheaper intervention now, or you can speculate on something that helps in the future at some indeterminate time, probably decades away, that will always cost more.
And to make another point against FSD as a humanitarian intervention. Looking at the highest vehicle deaths per capita (or per no. of vehicles), it over represented by developing nations. What's common to them is poor infrastructure, unpaved roads, older vehicles with less safety features, lack of government enforced safety standards, lack of road rules and enforcement, etc. Worldwide road deaths will be more affected by regulatory interventions, capital spending, etc. FSD won't make a real dint in this number.
https://en.wikipedia.org/wiki/List_of_countries_by_traffic-r...