Red Squirrel
No Lifer
It's not the least bit odd, it makes perfect sense to everyone on Earth except OP and I guess you. The battery packs are proprietary from brand to brand, but interchangeable within a brand. If you have a cordless DeWalt drill with a battery pack and a cordless DeWalt circular saw with a battery pack those batteries can then be used with a reciprocating saw, jig saw and double thrusting dildo. If you need a battery pack you buy one and if you already have one you're not wasting money on duplicates. Why is that difficult to understand? It's the smart way to do things and it makes things easier for the consumer. They're not trying to rip people off, they're intentionally NOT ripping them off.
Idealy you want at least 1 battery per tool, and possibly some spares. So it makes sense for it to come with the tool, and I've never actually seen it otherwise.