- gift cards involves getting in a car and driving to a place to buy them, which introduces annoying logistical issues
- the purchases made on a single card are linked together, so you have to keep track of cards you use for x store and what cards you use for y product (this is also true with bitcoin though, which is why I prefer other more privacy-focused cryptocurrencies)
- with gift cards there is a very high chance that your funds will be rejected or flagged as suspicious. which also limits the amount you can spend to around 100-200 dollers, since any more risks having all the money you put into that card flushed down toilet
I do personally keep a couple of gift cards on hand for the rare occasion I find myself needing to pay for something online and there is no alternative vender that accepts cryptocurrency (usually event tickets or membership subscriptions), but its a pain and I much prefer paying for things with cryptocurrency.
Cryptocurrency is an unregulated and environmentally disastrous ecosystem rife with monopolistic vender lock in, fraud and abuse, and little to no accountability or legal recourse for end users. But that's also true with the credit card / debit card / other electronic payment ecosystem.
At least with cryptocurrency I get a modicum of privacy.