Except, in the case of the 747, that pin is a nosegear steering cutout pin used by the ground crew during pushback, NOT the landing gear safety pin that prevents the gear from being raised. The gear safety pin is a preflight item, and should NOT be installed during normal ops. It is well hidden, high up in the linkage in the nosegear well. The steering cutout pin is installed near the intercom box just above the nosegear tires, and is usually installed on the ground.
I don't know how many other airliners have the steering pin.