Photoshop definitely wasn't intended for the wide variety of use-cases it now supports, but it is definitely the front-runner for digital painting, 95% of concept artists/comic colourists or similar artists I know or have seen use Photoshop. Krita looks fantastic, really capable, but I haven't had a chance to try it, mainly because all of my brushes and settings are in Photoshop.
Most designers I know will draw on illustrator and maybe finish up in Photoshop. Since Photoshop is a sort of common baseline in the industry it's used as a general tool to aid in the finishing of artwork even when said artwork is not really in its domain.
Illustrator seems widely used in brand and web design alright, but for example concept artists and comic artists I know never leave Photoshop, start to finish.
