They rather famously switched to an Xbox controller for their rolling drones, and for their submarine controls, because they just work better. For quite a while, military-issued camelbaks still had bright blue caps because the contract to custom build the systems hadn't been settled yet. There are in fact plenty of electronics that they use that are not purpose built, that are bought more or less off the shelf.
All of that said, I still agree that the US military is unlikely to allow off-the-shelf drones at this time. Parts availability is the driver there. Its better to pay a contractor $3k a pop to buy a bunch of a DJI Mavics, spray paint them olive drab, and issue them to each platoon than it is to give every platoon $3k and say "go buy a drone", because then you can buy 6000 of the same replacement rotor or whatever.