Thieves and stolen Diamonds

How many movies can you name off the top of your head where the villain is a thief trying to possess a rare and valuable item? While I'm betting a good number are bad live action movies, it seems to come up a lot doesn't it? Even some good movies like Disney's Tangled have this as at least a plot point. (A stolen crown is the motivation for one of the main characters for the first half of the movie.)
It always goes that the villain manages to steal the item from a museum and is trying to sell it to other criminals, but the hero stops and captures them.

But, have you ever really thought on this?
Let's say the item is a very large diamond.
So the thief manages to steal the diamond... Problem is, realistically, no fencer or criminal mastermind would want it because it is incredibly hot. They wouldn't even want to be near the thief who took it for fear the police would follow the thief to them. Meaning, to the thief, the diamond is worthless.

That is the flaw in this whole plot; The thief has stolen something that is worthless because it is stolen.

But, for sake of argument, let's say that the police cannot track the diamond...  Unless they are a Bond villain who is planning to use the diamond as a focus for their death ray, the diamond is too large to be of commercial value.
Think about gold. We value it highly because it is pretty and somewhat rare. However, if we didn't care that it was pretty, we'd be using gold as wiring instead of as jewelry.
Diamonds have very few uses outside being installed in jewelry. Extremely large diamonds can't be installed in jewelry unless cut or split in some way.

So, the thief has a diamond that he can't sell in it's normal state. He could find a jeweler that just cuts the diamond down without question so that it may be used in jewelry and is unrecognizable to the previous owners... But then the diamond goes down in value because it has ceased to be the diamond he stole. The cut diamonds have the same value as other cut diamonds, but the thief's diamonds had higher risk to them with less reward.

In the end, one thing holds true about items of value that are stolen: they only have value to the legitimate owners. But, even to the owners the Diamond is worthless. It is just pretty to look at, and worth no more than a wooden sculpture in principle.


But, this is an easy plot for quick cash-in movies, and is not going to die easily... So better to just give a better reason for stealing the Diamond than just "it's worth a lot of money."
One possibility is the Bond plot, where the diamond is for a death ray. Or a scientist wants it for a telescope but can't afford to purchase it.
Anything is better than just stealing a giant diamond and trying to sell it to criminal overlords because it is pretty.