These are firm airline policies which an agency cannot override. Agencies such as Expedia simply abide by them. And when you have a problem such as this, your best bet is to pursue alternatives with the airline's agents on the spot, not the agency. If you get charged extra, it's because of the airline, not the agency.
Another reader, annoyed that his baggage didn't arrive on his flight, asked about delayed baggage:
"When my bag doesn't arrive on my arriving flight, what are my rights to compensation? Does the airline have to pay for interim expenses?"
The short answer, at least for most airlines, is, "They promise to get your bag back to you as soon as possible. If you're no longer at an airport, they'll deliver it to your home or hotel, and most say they'll cover interim expenses."
Here are the exact statements from their customer service plans or contracts of carriage:
Thus, most lines help out with essentials when your bag is delayed. But that's all you get – no additional cash, voucher value, or frequent flyer miles. And, obviously, that "reasonable expenses" limit means reasonable: No Armani suits or Dior gowns.
Another reader experienced a problem that I would not have expected:
"I had a nonrefundable ticket on JetBlue, but two weeks before my flight, the airline changed the flight schedule. I had planned a meeting at JFK during my connection layover, but the new schedule gave me no opportunity for the meeting. So I cancelled the flight and asked for a refund. Imagine my surprise when the airline refused to give me a refund. Instead, it offered full cash value toward a future JetBlue ticket, which I could use for a ticket for anyone. Is this right?"
My short answer here is, "No it's not right, but airlines do a lot of things that aren't right."
I checked the contracts of carriage for the eight largest lines, as above, and found that their contract provisions regarding schedule changes are all about the same: