The watch is connected to your hand, it's never hands free. You have to move your hand to turn it on in the first place. The point is some people are willing to exchange 'Hey Siri' for more battery life because they don't find it to be an extremely necessary part of its function, since you can do the same exact thing by pressing a button for one second.
I can understand some people are going battery crazy by turning off haptic, etc, which is overboard and unnecessary. But turning off 'Hey Siri' is a very minor change and doesn't take away from the experience--at least for me.
*Sigh* come on man.....
Handsfree is an adjective describing equipment that can be used without the use of hands (for example via voice commands) or, in a wider sense, equipment which needs only limited use of hands, or for which the controls are positioned so that the hands are able to occupy themselves with another task (such as driving) without needing to hunt far afield for the controls.[1][2][3]
Listen, if you want to turn off features, knock yourself out. But by saying there is no difference between pushing a button and just talking? You're being disingenuous.
Perhaps you don't understand the value of this feature? Maybe that's why you don't miss it.