Passengers leave a larger margin because they are requested to be at the airport for 2-3hrs before departure. The margins crews have to leave due to the airlines' policies and working hour regulations are much smaller which means that a small traffic delay has far less of an impact on a passenger who will in turn just wait at the airport for the flight. The crew on the other hand need the time allotted to them to work and prepare for the flight; they don't just sit idly by waiting for the departure time like passengers do.

Basically they are on duty and working as soon as they arrive, so they plan for those times accordingly. There are comfort margins and I'm sure your crew did their best to get out as soon and as safely as possible. Again, by no means KL specific and most airlines will encounter this. It's regrettable that this happened to you and all the other PAX on your flight. Next time you are delayed arriving at the airport due to the snowball effect (no pun intended) of situations beyond your control, I hope that the airline is somewhat more understanding than you are to this situation.