The problem with removable batteries is that you sacrifice water-proofness. That's why iPhone batteries aren't removable: Apple found that, on average, people prefer a water-proof phone over a replaceable battery. If you make the battery to removable, you can't use sealants anymore, you're just relying on a gasket.
Personally, I would rather have a phone that can handle being dropped in a sink full of dishes and am happy to pay $80 every 3 years to have the battery swapped.