My understanding is that they have a specially in-house designed/built machine for radiusing necks, and it's specific to guitar necks. It's not like they can save up box tops and send away to "Fretboards 'R' Us" and buy something in "Size Fit". Or, maybe they could, but it's not worth the investment. I'm sure the bass parts business is nowhere near as large as the guitar parts side of it, so they just choose not to get too crazy about it.
It is a business after all, so they have to look at ROI (Return On Investment). If it's too small, then it doesn't get serviced. Kinda like Microsoft. Doesn't matter if there's a market for good operating systems - it's too small to service relative to their normal output. So, they leave it to the Unix/Linux crowd to deal with the scientists/banks/insurance companies/ISPs/embedded systems/and the like who are more particular but dramatically smaller in number.