Of course limiting oneself to one thing gives less options than two things, but this "tool" analogy (that keeps coming up) is not fair. Better would be to compare to the woodworking shop itself, where there are many tools that together solve a wide class of problems. You can run multiple shops if you like, with varying combinations of tools, and large overlap in the problems they can solve, but the overhead involved is not the same as choosing a screwdriver to screw and a hammer to smash.