Why not just use the 18650 cells?
That's a great option for battery geeks - not so much for normal folk. Why?
Normal folk are easily duped by counterfeits, false capacity claims, poor quality etc, and don't have the means to verify such. Especially in multi-cell arrangements.
Vape-shop rejects, pulls from used laptop batteries etc, that can be generally unsafe in unskilled hands is the reason I wouldn't let my friends use just any old 18650 they could get their hands on.
Personally *I* would love it, but if I were thinking like a manufacturer with safety of my users in mind, I wouldn't go there. Not because of the user or the technology, but from the wide variety of unsafe JUNK and shady vendors. Or unsafe DIY'ers that think pulls from crashed EV's is a good idea.
As a manufacturer, now you have to provide *individual cell* protection, not knowing if users will use protected cells or not, mix and match these cells from different flashlights, vapes, etc etc. Waaay too much liability.
That's why I like the idea of manufacturers getting out of the battery biz by using a Motorola battery. (or Moto shaped clamshell for AA's). A manufacturer can't control the quality of the knock-offs, but at least the user who buys a real Moto should be assured of both quality and safety in charging. Would probably release the manufacturer from that legal side of the issue and get the product to market even faster.