For inbounds, as I only too well remember after 6 hours in the seat in goon bag, jacket and all the rest of the gear the exploding bladder scenario may be taking all the more mature aviator's concentration.
I once got held on left base for 15 mins (due controller training, she was following the rules, not squeezing us in the way the experienced controllers would) and then got a complaint from both company and ATC for leaping out of my seat for a pee on the grass at the tower side of the den. It was either that or find out how good my suit was from the inside!
As for the outbounds I do remember siting at one of the W holds watching the taxi fuel burn off and rapidly re-juggling the plan. It sounds from this thread that the pressure is coming on to burn a lot less gas.