Phone cameras are extremely wide-angle so everything is in focus and there is no natural bokeh. To add bokeh, you have to separate the subject from the background, and then also determine how far different parts of the background are. This requires very advanced AI for non-trivial images (see the imperfections in Photoshop's "select subject" tool), which Apple is actually still doing (that's what portrait mode is). But if it's not perfect, it quickly becomes worthless, so in short, they are doing it, but only the most advanced companies can try.