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.
Nothing wrong with asking - treating cabin crew as humans (be nice, be polite, don't stress them if you see they are busy, wait for your turn) will get you a long way. You'd be amazed what is possible. One nice passenger offsets many rude ones - be the nice one!