At a bakery, people take a number instead of standing in line - and are called when it's their turn. Why does the same principal not seem to apply so easily to the call center (ie/ virtual call queuing/agent call back), when the technology exists

At a bakery, people take a number instead of standing in line - and are called when it's their turn. Why does the same principal not seem to apply so easily to the call center (ie/ virtual call queuing/agent call back), when the technology exists?