I sell them to clients of mine (families). I mainly do newborn, children, & family photography. I also do headshots. They all buy the digital files and then do with it what they want...share on social media, print out photos, canvases etc...
The problem with that is that you have no control over the quality of those prints, and your reputation rides on it. I suggest you offer packages tailored around their uses of the files, if you really must licence the digi files, and size accordingly (which is not just to do with ppi/dpi), plus recommend a print supplier whose quality you have checked.