One of my kids has two of them. (no, he only plays one at a time) He's a drummer and he enjoys the portability of the cajon for small acoustic jamming.
It wouldn't really be my thing, but I could see a number of possibilities. A non-drummer could use it to lay down a basic rhythm track to show the drummer how they want it to feel. It could be used as a percussion part along with a kit. It may be just right for that acoustic crooner that makes everyone think that you're deep and profound.