It could become more efficient and sometimes crew do bend their T&C's to suit them.
I have seen crew begging over the desk to let them keep the rest of their trip (I believe it was to GVA) even though the inbound flight had been delayed and it meant they had to go straight to the aircraft. No problem for them! On another occassion, the crew refused to do it because it was "only a there and back to MAN", and the inbound trip had been delayed with only a few minutes.
Still, these allowances and payments do make up a HUGE amount of the pay check, and some months are a real struggle (spare me the comment of going shopping and using the crew card). If you get a month of DEL, BLR, MIA and IAH, it's not that easy!