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?
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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
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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.
There are "extra" meals so you can certainly ask.

If you are say, a first class passenger, the extra meal will be given to you almost as a matter of course if requested. You have "first dibs" on this (and other) privileges.

If you are "coach" class, your request will be granted more often than not. A problem might arise if first class, or other coach passengers asked ahead of you, and they're "out." This might be particularly true of a certain meal, as opposed to "meals" generally.

The alternative to giving away an extra meal is that it is thrown away. Most attendants would rather give the meal to someone than to discard it. You will not be charged.

Note: This answer does not apply to "food for purchase" situations. Then you do have to pay for each meal that you eat.