SS frets aren't much more expensive to buy, but they're a bit harder on the specialized tools that you need to do a proper refret. End clippers and the like will chip much easier, it takes a bit longer to level and polish them. If people played guitar more they would be demanded as standard equipment on every guitar sold . . . but most will buy a guitar and then barely/never use it, so manufacturers don't seem see a reason to put SS frets in guitars.