Is this just what was in fashion?

Yes, essentially. There is a fashion to face shapes and facial features, just as there is to hairstyles and body types. The type of face considered most attractive for women around the end of the nineteenth century and bleeding into the twentieth was much rounder than the ideal today: a soft jawline, full cheeks, and less-defined cheekbones. Gaby Deslys is an excellent example of the fashionable face, as are Billie Burke and [Camille Clifford](https://commons.wikimedia.org/wiki/Category:Camille_Clifford#/media/File:Camille_Clifford_(Mrs._H.L.Bruce%29(Mrs.J.M.J.Evans%29(LOC%29.jpg). Coming forward into the 1910s and 1920s, there are [Mary Pickford](https://commons.wikimedia.org/wiki/Category:Mary_Pickford#/media/File:Captain_Kidd,Jr(1919%29-_Ad_1.jpg) and Clara Bow to compare with. And on the other hand, actresses of the 1940s and 1950s who embody a different ideal: Lana Turner, Judy Garland, Grace Kelly. You can especially see this change with images of the same actress during different time periods: Greta Garbo in 1925 and 1939, for instance. The 1940s and later standard of beauty put more emphasis on the chin and cheekbones.

Now, something being fashionable doesn't mean that everyone will necessarily adopt it, especially when it comes to elements of physicality that cannot be easily changed, but it does mean that the models and actresses who make up a huge portion of extant images will look that way, as they were considered screenworthy in their time in part because of their conformity to the beauty ideal. It does mean that people would attempt to emulate it, however - in this case, dieting or not dieting to cover or hide the cheekbones, wearing or not wearing cosmetics, having a haircut that accentuates the roundness or gauntness of the face, etc.