If one were to look long and hard enough for the specifications on USB Power Delivery version 1.0 then you will see a means by which a compliant source and sink could negotiate up to 20 volts at 5 amps on a USB-A connector. There were no extra pins for this negotiation, the communications was by BFSK modulated signals sent on the Vbus and Vgnd lines.
Use of USB-PD on USB-A was short lived, and I am not aware of seeing any devices that operated in this manner. One issue I heard was that the communication was not well isolated and so one device could have this power negotiation induced onto an adjacent port and that device would see it's voltage change even though it made no such request. This could damage hardware. Another problem was that the cables would have to be certified for this higher voltages and current, meaning the cables would have to be built for this as well have a means for the USB controller to know that the cables met the spec.
USB-PD 1.0 was not required for USB-A but it was required for USB-C, and that likely affected adoption. USB-C had a different means to handle PD negotiation, the Configuration Channel, which used a different protocol called BMC. USB-C could optionally support BFSK on Vbus for communication with USB-A ports which meant that to assure compatibility the cables would have to translate the PD negotiation, or do no PD negotiation at all and supply only the default 5 volts.
At the same time USB-PD 1.0 was introduced so where a couple competing systems for negotiating power over USB-A. USB-PD was a bit late to the game and so QuickCharge and others took over that space. I believe that they simply negotiated the power over the USB D+/D- lines. This violated the USB spec, or perhaps not, and because it was in a grey area the USB specification enforcers could not, or would not, do much about it.
Not many people cared much of USB-PD until version 2.0 and it was required for USB-C. USB-PD v1.0 was technically supported but not much people even cared. PD v1.0 was limited to 2 amps in certain configurations and so that's why you will find older 10 watt USB-A power supplies, which used USB-BC as an alternate means to negotiate power. Anyone wanting more power seems to have moved on to USB-PD v2.0 or some third party protocol like QC or VOOC. When USB-PD v3.0 came along all features from USB-PD v1.0 were gone and third parties started to incorporate at least some support of USB-PD into their specs.
The means by which these protocols negotiated the power transfer was by communicating over the D+/D- data lines, rather than the USB-PD way, use of the data lines for power negotiation meant the cables were not capable of transferring data. Some used the D+/D- lines to carry power as well.
The latest USB-C spec, USB-PD spec, and perhaps other USB specs, makes use of a third party power transfer system a violation of the spec. That's not going to make it all stop because there's plenty of old gear out there, and not all manufacturers care much about complying with the USB spec. Those that do care about compatibility will support USB-PD fully as well as portions of the third party spec as a selling point and/or means for a smooth transition from old to new.
The direct answer is that the pins are there but USB-PD no longer uses them. Some USB-A to USB-C cables have circuitry in them to convert third party power from USB-A to USB-PD for providing power to USB-C devices. Personally I'd stay away from them but for people with Android devices this may be something of a necessary evil.
Explaining this is in a way a history lesson of USB-PD. I know I didn't get every detail right, but the highlights are there. If dates on when these things happened concern you then maybe someone can come along to fill that in. As I see it the wired charging boils down to the old Apple and USB-BC on "dumb" USB-A chargers, some "smart" USB-A chargers use some mix of USB-PD and their own protocol, and USB-C chargers are going to be USB-BC. A new development is USB-PD PPS, or Programmable Power Supply, which means they can vary the output voltage by small increments. With PPS there's plenty of room to support third party charging which may or may not technically violate the USB spec.
