I also wondered the same until I saw that Rheinmetall produced that type of defense system you describe (I think in 2024 or so). And I think that except for Rheinmetall, nobody gives them this type of weapon (seems other countries have something similar), but it's probably a handful of them deployed in maybe very few locations.

I don't think it's that simple to build it, otherwise they would have all done it.

Edit: it's called rheinmetall skyranger.