There are quite a few games which were developed primarily with kb+m in mind, but also have some controller support. So you might hit a menu or gameplay section that really requires typing or something.
On steam deck this works pretty well with the pop-up keyboard, but a physical keyboard is always a bit nicer
When they say something like “60 days battery life” what they mean is using the device for half an hour everyday for 60 days.
OP is arguing that it would make more sense to just say the continuous use battery life, which in the above example would be 30 hours (60 × 0.5)