Why not sell just the fcu/fci?

Getting really frustrated with the lack of availability of just the fci or grip options with the fci. Why hasn’t Ruger started selling the unit alone just like the p320 or p365 fcus? Alls I want to do is put an fcu in my sub compact frame and compact frame then be able to swap between them without performing surgery on the thing and only needing one optic. Mr Ruger gonna get a big old knuckle sandwich.