Like /u/Monstrosity already said, photos is great use. Dealing with it rn, want to transfer bunch of my pics to my pc and it takes forever and fails a lot trying to do it over cable so just putting it on SD card and then just plug the SD card into the PC is way easier. Solved it by installing sync thing so that works for now. I also like to store all my music locally so I don't have to worry about bad signal or anything like that, also some movie and books for when bored waiting or something. I definitely love having stuff locally plus it's just much cheaper large storage than getting a phone with bigger internal memory. So yeah there's tons of uses why you would want an SD card. Makes lots of things easier and easily transferable. Same with headphone jack, don't have to deal with connecting stuff guessing the pairing code if it's one or the other default one. Just plug it in and done. Also don't know how it is with modern phones but you can listen to radio using the headphones as anténa so definitely another use for someone that would want that.