My guess is that it has to do with the battery losing its ability to hold charge with time. It makes sense to engineer a massive new battery for the iPhone or M

My guess is that it has to do with the battery losing its ability to hold charge with time. It makes sense to engineer a massive new battery for the iPhone or Macbook, but these peripherals don't have the same volume or margin cushion to absorb the cost, hence off the shelf battery technology. Also, I think most people expect to change out a computer every couple years, but a mouse is supposed to last longer. If the thing became incapable of holding charge after 18 months it would get customers riled. After using a Magic Mouse for 6 months, I can say the rechargeable battery station is a must buy, I have to change my MM batteries every 3 weeks or so.