I think this question has come up before (maybe it was on the Vestratto Discord), and it comes down to:
- unregulated 18650s are dangerous if you don't know what you're doing
- Vestratto wants to reach the medical market (I believe this was always the goal)
- someone else has already solved the problem of making a rechargeable battery pack capable of powering the Forge
- it's still more flexible than a factory-installed battery
- one could, if one chose, bring a Milwaukee battery pack on an airplane