these things can fly between buildings and in amongst trees they...

these things can fly between buildings and in amongst trees they are highly maneuverable - height and speed are not the points - as it is with civilian planes - they also cvaryy a few hundred people - with these jetpacks its more they fly and are maneuverable meaning ground based obstacles are no issue - swamps, deserts, lakes, forest, whatever... or a vertical climb if required.

Imagine 100 of them taking off from a ship of a surfaced sub - there's few helicopters on subs!

Every vehicle has its place - some work well in one action but not another - you use them to their strengths rather than compare them to existing vehicles.