To follow on from kempus (dude) and Rainboe,
Once on final approach and disconnecting the auto pilot, you do not need to fully disconnect the auto throttle. By “de-selecting speed” i.e pressing the “speed” button on the MCP, “ARM” is displayed on the FMA’s. This means that you have control over the power settings just like you would have if you had pressed the auto throttle disconnect buttons, but in the even of a go around, the auto throttle system will kick in and the thrust leavers will advance automatically to go around thrust once TO/GA is pressed. From memory (it’s been a while since I flew a Boeing) it will give you the flight director “pitch up” indication on the go around also. If you just disconnect the auto throttle fully, you have to advance the thrust leavers yourself in the event of a go around.
Just got to make sure that it’s “speed” and not the “N1” button next to it that’s pressed. That can make life amusing on short finals!
(I think that’s why it’s not recommended by Boeing, please correct me if I’m wrong.)