Last time I had a flight with too much fuel, they had loaded fuel to be able to go around weather enroute, but then the weather got even worse so they cancelled that flight and the plane was given to our flight. It wasn't anyone's "fault" that it had too much fuel, in fact it was because they were doing their best to get a flight out safely.

As it was the options for our flight (small station) was remove passengers or remove fuel - no plane to switch us to. They were getting ready to IDB 10 passengers, when they got permission to take the delay and remove fuel. Thankfully everyone on our flight had long connections as it took quite awhile to remove the fuel - so it most likely was much faster to switch planes.