I guess that depends where the button is located. If you are sitting down on your couch and forgot to turn off the light it definitely beats standing up and walkin back to the door.

If the switch is within reach anyway then I totally agree that a voice command is more cumbersome than just hitting the switch

Decent switches are relatively quick. It's not instant, but in my house close enough that I open the door, say "Alexa turn on the lights" and lights turn on before I close the door behind me.