These days, many people work on a laptop. On a laptop on battery-power, running and rerunning the slicer for every change does affect how long the laptop will operate before the battery runs out. Hence "waste of resources".
Well, as the laptop is standing next to the 3D printer which almost certainly runs not on batteries, there should be a power connection somewhere close.
I'm actually with you concerning the re-run of the whole slicing process. I recently suggested that for e.g. an object shift, toolpaths would not have to be recalculated but just translated by the shift distance. The answer I got indicated it's a good amount of work to achieve that...