You also do so in the UK and virtually every other country I can think off.
As an individual if you mine you have to record the value as it was at the time of mining if you buy you record it at the time of purchase and you pay capital gains if you exchange the crypto for fiat currency or goods or services directly on the difference between the values. It gets more complicated since you can’t select an individual currency unit form your wallet but atm you are allowed to use creative accounting for that.
The fact that you have an allowance doesn’t mean it’s not taxed and if you have any substantial amount you’ll blow throgh that allowance pretty darn fast.
The same goes for many other assets you pay cgt only when the profit is realized.
* Capital gains in excess of £11,300 * Disposals (sales) in excess of £45,200 * Losses that you wish to claim
https://www.gov.uk/capital-gains-tax/work-out-need-to-pay
Worth noting e.g. if you receive stock under US company schemes and sell even if you have already been taxed on the gain versus FMV as income. You can be in a circumstance where the taxable gain is under the threshold but disposals are high.