wow, that was a sour response...
anyway I can see where the OP is coming from. In my experience US airlines will tell you in advance what their expense reimbursement CAP is.
It makes sense to ask nonetheless. I see no reason why one should feel so strongly and be so get aggressive about this
; it's just common sense.
Depending on where you end up without your luggage and how long it takes them to return it to you, the expenses may actually build up quite quickly...
For instance Delta cleary states on their website:
"...Delta requires that receipts be presented for all reasonable expense reimbursements incurred due to the delay of your bag(s). Reasonable expenses generally are $50 per day for the first 5 days the bag is delayed. The guidelines for reasonable expenses are NOT daily limits or a cap and additional expenses may be incurred and should be handled on an individual basis up to the limit of liability. Any disbursements will be deducted from the final settlement if the bag is not located..."
In another occasion copy of the reimbursement policy (stating the max reimbursement) was provided to me after filing my baggage claim at the airport. The agent handed me a copy without having to ask. The flight was operated by AA...
Frankly not letting your passenger know this information in advance is quite unfair and appears as a sneaky way to try to get away from reimbursing anything, as there is no certainty as to what "reasonable" according to OS entails..