Came with nipples and worked out as the cheapest price available
Again though, it’s not just about coming with nipples, it’s whether it’s the right ones for you.
All spokes will come with nipples from the manufacturer. Not too sure on Spain, I know CX-Rays come with ‘Polyax’ (alu). For DT Competitions silver spokes come with brass, black with alu weirdly.
So yes, JRA are keeping the nipples and potentially selling them to you as an extra, but they’re also not selling at retail, splitting packs etc, so there’s a bit of give and take.
Personally I’ve used black nipples on my last few builds, brass ones for some road wheels, and alu for a pair of light road wheels and light mtb ones. All were purchased independently of the spokes. I’m fine with that, don’t need hundreds of silver nipples I’m unlikely to use.