First of all there can be connections where you have to run to make the next flight. After all DL is a hub airline.

I prefer to wait in the CRC or the lounge rather than sit another 30 minuttes on the plane.

In Europe it is common to board first class last, so the passengers can enjoy their time in the lounge. You also find the flight attendants won't allow passengers to store their luggage on first class if they are not in this class. I wish DL would do the same thing.

It again leads me to a problem when you try to leave the aircraft. When in first class you have passengers from the back trying to push their way through first class to get out of the plane first. Again, you see on the European carriers that the flight attendants holding coach passengers back until the first class has exited. Another service for DL to learn.