Curved film planes were very common in low-end roll film cameras and even 35 mm simple cameras.
This is because they improve the image quality of a lens with a spherical focal surface, as is the case with the simplest lenses used in consumer cameras back in the day -- the meniscus. Meniscus lenses were common as far back as wet plate days (1850s on), and were popular because they were cheap. Kodak sold the Vest Pocket Kodak with an achromatic meniscus, but did what was necessary to use a flat film plane: installed the lens concave to the world, behind the aperture and shutter.
Later, for marketing reasons, meniscus lenses were often installed the other way around, convex to the world, which allows placing the lens in front of shutter and aperture and avoids "the lens has fallen off!" conversations at the camera store. Unfortunately, that way 'round a meniscus has a curved focal surface; this was compensated, especially in rectangular frame formats, by constraining the film surface to a cylinder which minimized the error, mostly confining defocus visible on the contact prints of the day to the extreme corners of the frame.
This "optimization" for lens cost is very unlikely to appear in digital cameras, however, because it would be offset by the costs associated with fabricating a non-planar sensor surface. Designing lenses with flat focal plane is old news; the Cooke triplet, Periskop, Rapid Rectilinear, and Tessar all have flat focal plane, and predate the introduction of roll film as we know it in 1901.
If you want to look it over, however, try to find one of the "plastic fantastic" 35 mm cameras that have been sold over the past fifty or so years. Ilford and Lomography sell them now as "reusable" (as opposed to disposable) cameras, at prices around US$30 to US$50, and cheaper examples can be had direct from China. All of these have simple meniscus lenses and curved film planes.