My employer contracts with a vendor that manages them. It's not expensive or difficult anymore. Even individual consumers can mint "virtual cards" with different time-based or merchant-based spending policies and limits for free, since like five years ago now. (https://www.capitalone.com/learn-grow/money-management/what-...)
You can add them to Google Wallet/Apple Pay. Useful for giving a family member a limited expense card, e.g. you can set up a "let my kid buy up to $X of food on weekends" card they can add to your phone.
