BOAC,
Very true. It is also worthy to note that the Captains signature is in the tech log. In many incidents the FO gets reprimanded/retrained the Captain gets the sack!
So 'conservatism' is, in many ways, a very good thing when you are just finding your feet.
The other thing to consider is that the job of a Captain is not 'just' to fly the aircraft there are many other external variables that have to be thought of. Not all of which are obvious from the RHS.
So give them a break, we are all there to achieve a safe operation.
W2P