I like to say that every camera or system has a "gamut" of photographic tasks that it can do well (or "well enough").
Yeh, that's exactly it. I've got a kit room full of stuff, and the cameras complement each other.
I've got a RED which is fantastic for video, has probably the best dynamic range of any camera I own, and the ergonomics for video are unsurpassed. (eg indicating RAW channel clipping live on screen). I
could use it for stills, it even has a mode for tagging still frames as part of a video feed. But it isn't comfortable in that role (eg don't think it can trigger strobes).
I've got a Hasselblad which is great in the studio but which eats a ton of light. I
could use it for available light shooting, but it is really outside its gamut.
I've got a GH4 which is great for the mountains. I
could use it for my fetish fashion photography, but it doesn't do that as well as the Hasselblad- it is one place where the lack of megapixels and slightly less than stellar skin tone rendition really matters to me.
I have a 7D which is reasonable for available light, but whose shutter is about to fail. (I know the sick shutter sound of old, having burnt out the shutters on several Canons over the years).
I decided to replace the 7D with an A7RII, rather than just replace the shutter, because the strengths of that camera seem to fill in the gaps in my kit lineup. I'm enjoying it so far. I shot an ISO 1000 pic which none of the other cameras in my kit room could have got without serious time to rig light sources (rather than quickly popping out a reflector).
Cheers, Hywel