Danbuster, tend to agree with you there.
I certainly do not rescind a jumpseat previously granted through the crew direct system, even to the extent that if my wife wanted to go somewhere with me
, she would understand the principle involved in honouring that seat to the guy who may have made plans and be depending on being able to travel having been granted it.
Where I do check with the other crew, is the late notice request - often at dispatch or by the traffic staff on the aircraft, where the applicant may be an unknown/ random, in which case I ask for the views of the other crew. Seldom have I had negative feedback, but it's the courteous thing to do.