What's a "leisure rate" for the hotel? They don't ask you the purpose of your travel. They revenue manage just like an airline does. Seeing how hotels are immovable, it's kind of hard to engage in back-to-back bookings. But if a hotel had a special "locals only" rate, and I booked it as a tourist using a fake ID, I would be engaged in fraud. Or if they required a Saturday night stay, and I checked out on Friday, they'd be justified in adjusting my bill.

Lots of big words. However, just because you don't like terms of sale doesn't make them any of those things. Delta has rules. If you don't like them, you have two choices: (1) don't fly them; or (2) convince them to change the rules. However, ignoring them is not an ethical or legal response. And for like the 800th time, no airline is ever going to press charges for ticketing fraud. Just like a baseball team isn't going to prosecute you for buying cheap seats and then grabbing front row seats that are empty - even though you're technically trespassing. They're just going to throw you out or ask you to go back to your seat., and they should.

Why not? It's a publicly available fare? All you have to do is tell them you're buying the ticket for your kid and use it. I mean, it's really honestly an arbitrary, outdated, unenforceable one sided condition, right? So just break the rule. That's your policy toward airlines after all.