Originally Posted by anc-ord772
Internationally it’s a hard rule.
For international flights it is a rule - Positive Passenger Bag Matching (PPBM). Passengers MUST travel on the same flights as their bags. If you decide not to fly - your bag gets pulled. However, there are some cases where your bag may not be on the same flight such as misconnect baggage. But this is permitted as the passenger was not in control of the change.
Originally Posted by anc-ord772
If you volunteer at the gate for a bump they always say no if you have checked luggage. Same idea applies to switching flights.
Domestically, you may get told its because of PPBM, but in reality there is no hard and fast rule unless its an airline policy. Carriers have much more leeway with baggage domestically. Unfotunately they don't extend that leeway to the passengers as well.