It's a good point, but in practice I have found some devices won't even power on with the 1.2v batteries. A good example being the Microsoft Bluetooth Mobile K

It's a good point, but in practice I have found some devices won't even power on with the 1.2v batteries. A good example being the Microsoft Bluetooth Mobile Keyboard 6000. The batteries don't last for 5 minutes even. Alkaline batteries last for months.