Assuming flights within the US...

If the delay is beyond their control (a claim they can often make, whether or not common sense agrees), they aren't obligated to provide much of anything. If it is clearly under their control (e.g. broken airplane), I don't think you have much legal right to redress either, but many airlines have customer service commitments that facilitate duty of care.

My approach is to book hotels myself in such situations (unless they are handing out vouchers in an efficient manner), and then submit receipts after the fact. About 50% of the time, I get reimbursed, and when that doesn't happen, some miles or travel credits often show up in my account.

I'm not really bummed if I don't get reimbursed though because getting good sleep is worth paying for IMO. But, this means that I try to keep the hotel cost reasonable (e.g. Hampton Inn instead of Grand Hyatt). This, austerity, itself increases the likelihood of reimbursement.