[Not a US citizen/resident; never worked in MIC-related area]

a). MIC is an industrial sector creating jobs, doing some R&D (which can trickle down into the civilian sector) and bringing hundreds of billions they do in exports into country; all of those seem benefitial for the overall economy. Of course those can be achieved in non-military-related areas, but so far there was a working machine - and a wrench is already thrown into the gears.

b). The last three years have shown that large-scale wars are still on the table and having a working and oiled MIC is much better than having a degraded one.