Question: I am just curious if last minute hotel deals is actually a thing. I am not a big traveler and have no clue.

But in theory if a hotel has a bunch of empty rooms for the current day, it would make sense to rent them at a reduced rate as opposed to letting them be empty.

Is this actually a thing that could be leveraged?

I am going on a road trip, and the last leg of the trip could take many variations on a moments notice and was wondering if this is something I could take advantage of.

Answer: 
A cabin crew member here...

In general, flight attendants will be happy to give you the extra meal after the service is done, because they know it will be [thrown after landing](https://travel.stackexchange.com/questions/19850/do-airlines-recycle-uneaten-unopened-pre-packaged-food/19852#19852) anyway. Out of experience, there are always some extra meals, at least one or two. Sometimes passengers simply do not take a meal, some other times there's just an extra meal or two loaded for whatever reason. In some other flights, there's a shortage actually. They usually cover for this by using the crew meals, and this is rare anyway.

Is it ok?
---------

Yes, nothing wrong with it, flight attendants will not think badly of you. As long as you ask nicely, of course. One more thing, all the meals usually get heated at the same time. Once heated they are good to be eaten for a certain time, then they can't be served to passengers. So, if you feel you want an extra meal, ask for it. I have seen so much food being wasted while I was sure many people were hungry but were shy just like you.

When to ask
-----------

When they are serving you, give them a hint that you would love to have an extra meal if it's possible after they are done. Personally, when this happens I might give them right away if I know that there are extra meals. Otherwise, I will just wait until service is done and then come back with the extra meal, or apologize if I couldn't find any.

Note: I am talking about full-service airlines. For budget airlines where food is bought onboard, you can pay extra and get more food. That's a different story.
I recall once that a special-order meal got mixed up and there weren't enough of them (vegetarian), so the cabin crew scrounged around and came up with a couple meals' worth of snacks and the safe sides of extra meals for that person, instead... and with the offer of more, if they were still hungry after. 

Obviously this was something of a special circumstance, but the point is that those snacks would still have been on the plane, if the original meal hadn't been mixed up. If someone asked politely, there's a pretty good chance those extra snacks, or the other portions of the extra meals, could still have gone to someone else if they were still hungry even on that flight.

The cabin crew usually do their best to accommodate requests like that if you ask politely. They may be willing to put in a little more effort, like borrowing snacks from a higher class, if they know there is a reason for the request - something like a person being hungrier because they couldn't eat before the plane for whatever reason, or needing a larger meal to balance their blood sugar or to replace part of the meal they cannot eat. It might matter how long the plane ride is (and thus, how long until they know you can find something else), or probably a whole host of reasons based on how someone looks or asks, and how urgent or casual the crew thinks the request is.