As others have said, the price is an issue. And for pro use they have been sidelined for a long time. Before TV & Movies I worked in commercial photography for a while - ads, fashion, product photos, material for websites, etc. Never once saw or heard of a Leica being used on a pro job. Mostly Canon, some Nikon & Sony, and then Phase One on big-budget or really technically demanding jobs. Fuji medium format (well, semi-medium format) was just beginning to creep in when I left stills. While in school I was doing journalism work and shooting for local magazines, never saw Leica there either. Mostly Canon, some Nikon.
Leica doesn't really do zooms and shooting macro or tilt shift on a rangefinder is impossible. So that puts them out of the running in a pro's bag. Unit stills photographers on movies and TV usually use some form of mirrorless, so you could do that on Leica, but I have yet to see it.
Where I did see them A LOT was from fine arts students and camera club guys in the school darkroom. I stuck to Nikon since I could share one big set of lenses on my analog and digi bodies.
They're nice, well-built, and not for me.