I use them for every online purchase.
Privacy.com allows me to create CC's as needed. Each card is married to only a single vendor, so a stolen number will be useless elsewhere. I can amend the spending limit on the fly, or pause the card, or cancel the card. It makes things simple when canceling a subscription when they can't "accidentally" ding your debit or credit card one last time. You can also create one-time burner cards.