Because we know what happens when you try to make an expensive thing that takes the place of several somewhat related other expensive things and can perform all

Because we know what happens when you try to make an expensive thing that takes the place of several somewhat related other expensive things and can perform all of their capabilities: https://en.wikipedia.org/wiki/Joint_Strike_Fighter_program#Cost_overruns https://en.wikipedia.org/wiki/Joint_Strike_Fighter_program#C... https://en.wikipedia.org/wiki/Joint_Tactical_Radio_System#Problems_and_restructuring https://en.wikipedia.org/wiki/Joint_Tactical_Radio_System#Pr... You end up with a super duper expensive thing that takes 15 years longer than you expected to build and ends up not being able to do the job of any one of the things it was intended to replace. There's a lively discussion on the front page about one of the examples above.