If cryptocurrency was actually used for purchasing goods/services it would be more tricky.
Some of the challenges:
* Figuring out how to classify certain trades (wrapped versions of tokens, bridging assets between chains, staking, etc)
* Making sure I have all trades tracked in the spreadsheet (there is automated software for this, but there are a number of ambiguous situations it doesn't hand well, hence needing to manually track it)
* Spot checking wallets to make sure trades weren't missed
If you do complex transactions thousands of times per year, it would be reasonable to expect (and in many places be a legal duty) to figure out how you'll be accounting for these transactions in your books before the first transaction is made, and keep up to date bookkeeping for these operations continuously - not just making some reporting long after the fact. Like, such activities are so clearly above the level where either you hire a certified accountant or become a skilled accountant yourself, that's table stakes for doing such things. You're effectively running a business, so you're required to act like one, you're not permitted (generally, depends on jurisdiction) to just wing it.
This is ridiculous, which is why most countries don't apply capital gains to currencies regardless of how volatile they are. Bitcoin should be treated no differently. You're already taxed on the income used to buy the currencies in the first place anyway.