An air screen is a better screen than any escort vessel. With an operational range of hundreds of miles, aircraft would be better placed to detect launch hostile low-flying aircraft and anti-missile missiles before it is too late.
As for governments, they generally follow their military heads advice (not to mention what companies like BAe Systems tell them to buy, building lots of semi-useless frigates is probably very lucrative)...
How long can you keep aircraft airborne and where will you base them if you have no carriers or small carriers. There are huge costs involved here.
Military folks across the world would wish what you said about government’s heeding their advice is true but they know it’s not.