In normal cases I mostly agree - you can just charge it while taking a shower or something that you do every day. That said, Garmin's battery life shines when you are using it on a non-normal day.

Overnight camping, and sleeping in a tent for a few nights is a good example. I'm not "taking a shower" and hence don't really have a great time to charge it. With my garmin I just leave it on, and it keeps working for the entire trip.

Same thing with other "adventure" travel, flying overnight, etc.