I know this is probably tongue-in-cheek, but if you wanted the serious answer:
GIMP:
Non-destructive Editing (it’s coming real soon!)
Vector shapes, not bitmap
Smart objects
Full CMYK support
Full PSD support (for collaboration purposes), hahaha
KILL ALL FLOATING SELECTIONS
Kdenlive:
Well, I actually do use Kdenlive. I’m fine with Lightworks too, and Resolve on macOS. But it’s lacking finer color grading controls, the interface is inefficient (being fixed in a future release), hardware-based decoding/encoding needs to either exist or be improved.
And the other big reason is collaboration with other Adobe users.