Because you can always make the argument “it should be slightly thicker for another x% battery life” on to infinity. But actually drawing a line and saying “it should be exactly this thick because this is the correct amount of battery life” is actually really difficult.

From what I’ve seen, people want replaceable batteries because they go through their battery a lot faster than the average person. That’s always going to be a difficult sell because now you’re talking about less than half of the market.