By "convenient" I meant in comparison with getting a foreign card for me, which involves bureaucracy and (by my measure) incredibly expensive travel. As for "picking a coin" - that is not really an issue, since swaps between currencies can be done instantly and very easily. And there are only a few major coins that are commonly accepted anyway (BTC, LTC, XMR and maybe ETH).

For people needing anonymity, giving up consumer protection may be an acceptable tradeoff. Same as with cash.

Pre-paid cards make sense because said cards may be unavailable where the customer resides, and either they can't (like me) or don't want to use a KYC method to buy them.

As for difficulty for the merchant - yeah, I agree it is a significant downside.

P.S. Fees are indeed a problem in Bitcoin at least, but Monero's are barely noticeable.