This is incorrect. In order to power off, one must first long-press the lock button, then select 'Power Off' from the resultant options screen. It is not possible to power off the device with a single inadvertent button press from within ones pocket, as you suggest.
The fact remains it's ridiculous to demand confirmation from yet another pop-up box while powering off when the user has already performed a two-step process attempting to do so.
I didn't suggest it is possible 'to power off the device with a single inadvertent button press from within ones pocket', although it is possible, see below.
What I was writing about was that long press brings up a dialog with multiple choices. Some choices may result in data loss (i.e. restart and power off), flight mode results in complete loss of connection (both voice and data).
Such actions have to be confirmed, so that for whatever reason are selected accidentally the user can cancel the action.
Accidental selection is possible even on a computer with a mouse, and it is much more likely on a touch screen, especially when phone is used one handed or on the move, so it is very important to protect user from data and connection loss.
Note that not all people use the phone with two hands or on a table, some take it seriously that it's mobile and use them on the go walking, or when riding a vehicle.
Would you like not to have confirmation for power off? Create an issue in Android issue tracker and eventually it might be implemented. Until then you may look for other widget or launcher what doesn't ask for confirmation.
The default action should protect the user, so I'd expect that even if there will be a choice to not have confirmation the default will be the confirmation.
FYI, an even longer press of power button powers off the phone without confirmation, so an RTFM would have resolved your issue.
For flight mode there are lots of widgets, maybe there are some what don't ask for confirmation. I haven't tried any so I don't know for sure.
