Huge argument in favor of interoperability of subsystems: if all the gadgets could recharge one another or had a common battery type, then your spares could be split among gadgets.

Bonus points if other bits of hardware could be shared. Extra bonus points for software interoperability (long shot).

They do have the same battery, the bb2590.

It's completely standardized for all modern military equipment.

The problem is that if you are going on a week long mission you need enough batteries to last a week plus extra in case something goes wrong.

Source: I'm a veteran.