Just to put things in context for the non pilots here.
The autothrottle is just a tool, albeit a very nice one to have.
On the 737 it is not required to be operational for flight.
It is not even required to be operational for a Cat3 approach and autoland.
Autothrottles do throw wobblies every now and then, whether caused by a faulty radalt or anything else.
Autothrottles need monitoring and that means hands on throttles at critical stages of flight.