As well, they're not nearly as ubiquitous as batteries in the standard sizes.

Phone batteries are fairly expensive if I recall.

I'd be happy if mine hired idiots, instead it seems to be a muslim family who knows dick all about electronics working in an electronics store... If you don't know anything about your product why you trying to sell it?

I'm guessing "You're going someplace where you aren't going to have access to an electrical outlet, but can bring batteries." Perhaps a bus, or an older airplane. Or you want an emergency charger in case the power goes out and you don't have a landline.