Because many people are not smart. If they buy a 65w charger and see only 60w being pulled they’ll complain that either the charger or phone is defective and want a refund.
I would like to see it as an option to enable, at the moment though I just have a few cables that measure/display this for me. It’s a useful basic troubleshooting tool with laptops and phones. If you plug them in and dont see any current or only 0.1w, you know there’s a problem with the device getting power.