"Throw a Dyce" if you ever hold me inbound and I am short of fuel I will reply with my available fuel (less final reserve) expressed in holding minutes so you can then prioritise.
I think its a dangerous practice for us all to start questioning ATC. They have enough to do and if the controller has held us...you can bet he is busy.
Its simple, if short of fuel - tell some one before it becomes a problem...otherwise shut up and wait your turn.
For outbounds it gets a little more tricky but to be honest I add extra taxi fuel based on the time of day to cope with this.
To answer the question as to why we all try and get airborne at the same time......its what the Oil Companys want...so its what they get. It needs ATC to some extent to grow some balls and impose some kind of slot system on us. That would definitley help.
DB