The Obama Administration decided to fine airlines that let people sit on planes when they are delayed, sometimes for hours on end, in an attempt to punish the airlines for somehow allowing this to happen. After all, it's a huge inconvenience and it's unfair to everyone in the plane.
So, what do the airlines do? Do they invest billions in new infrastructure and expand logistics, do they implement new ways of avoiding delays? Do they turn around and bill the airports for failing to invest to handle higher levels of traffic?
Instead, they will simply cancel the flights instead. After all, it's the logical thing to do.
Seriously: the Obama Administration hasn't got a clue. They really do appear to believe that because the airlines can't always handle breakdowns and logistics problems that lead to massive delays (and that they don't return to gates to discharge passengers is because they're not allowed to without everyone having to go back through security and return their baggage, plus gates are in use...), that the airlines should be punished, punished because the poor schmucks on the airplane are inconvenienced.
This is the logical thing to do for the airlines: it avoids the fines, makes it clear to the passenger that the airline can't fly as planned (regardless of the reason), and continues to inconvenience the passengers.
The real reason that flights are delayed and people sit around on them for hours on end? Because the flying passenger only wants to pay for fuel and depreciation on the plane and not for infrastructure: landing fees don't cover infrastructure costs, only handling costs.
If no one pays for the needed infrastructure - additional runways, additional logistics, more employees - then the infrastructure won't be built. Given the incredible and absurd delays for building additional runways - it's a safe venture that lawsuits and lobbying eat up more of the budget than the actual building of the runways - it's no wonder that airports are under-dimensioned for the traffic that they bear (the delays always happen at peak times...duh).