It makes sense when you think about it. If you made a huge capital gain and then "lost" it in Vegas how is that different than "losing" it via other means?

Also, if this wasn't the case, it'd be a massive, gaping loophole. "Oh, I settled this stock in another currency, so I don't owe taxes yet/ever".

There are some situations where it maybe there should be an exception. When employee stock options are exercised, that's usually considered a taxable event, even if the shares aren't liquid (like in startups). This means you'd have to pay tax on something that you have to hold and could be worthless or forcing people into these events because the options may expire.

But for gods sake, whenever you "make" decent or life changing amounts of money, talk to a lawyer and accountant. There's so much misinformation about taxes out there. I used to work for a forex company and people, especially expats, would constantly move small amounts of money because they thought that they'd have to pay taxes on importing money into the country. They didn't realize that the forms they'd have to fill are only for reporting to deal with laundering. They could have just moved their money in one simple swoop.