Can a thief benefit from stealing Bitcoin?

When I think about all the stories about thieves stealing Bitcoin, or hackers extorting people for Bitcoin, I remember the fundamentals of the technology: it is a blockchain, and that chain ensures that you can know about every transaction. So, if a thief gets some amount of Bitcoin, and then exchanges it for fiat currency, or uses it for some other purpose, those transactions can be traced, yes? The use would betray the user, and lead to their capture.

Am I off-base here? If the thief did nothing with the Bitcoin, they gain nothing for their effort (the victim loses the Bitcoin, so a revenge plot would fit this scenario).