Safety is always the first objective in aviation, it's the foundation of everything we do. After that comes efficiency etc. ICAO homepage puts safety as the first objective:
https://www.icao.int/Pages/default.aspx
That being said, everytime a change is made, people are looking at the lowest (cheapest) possible solution, and start there.... then upgrade it until risk is eliminated or reduced to an acceptable level (there's always a risk). Once you get there you have a solution that is both safe and low cost.
Noone slaps class A airspace over everything and erects control towers at even the smallest airport if not needed... cause the safety benefit would be none and it'll be expesive as hell.