Back when Mp3 players were a thing (before the iPod) Archos were making an MP3 player which took 4 AA, and the mail list for alternate runtime (rockbox) was full of discussions about NiMH trickle charging, approaches to maximising battery life, as were Apple Mouse conversations. People went wild for the most long lived, fastest recharge AA.

In some ways, I think it's a shame we didn't go to consumer goods run on Lithium batteries but in this form factor, with discrete charge management cards. So for instance, replacing the batteries in a Thinkpad could have been commoditised.

Bagged cells are damn good for small devices, but they do make it harder.

My Minidisc players were equally 'my battery, my form factor' as are most digital cameras. I guess some people (Dyson) cannot go past the opportunity to make accessories and replacements bound in them, at their price. After sales income is big.