[drrotmos]

You can still make a device with easily replaceable batteries water resistant (or even water proof), but it's easier (read: less bulky) to do it with a non-replaceable battery.

Compactness is definitely a major tradeoff though.

[guerrilla]

Yeah, my Galaxy Xcover is IP68 (dust/water resistant) and the battery is trivial to replace. I think the situation is the same for CAT and other rugged phones.