Mandating wireless charging is still a bit of a stretch (it's not popular yet, so would be a short-term cost and manufacturing increase), but wireless charging is mentioned in the linked article as something they should look into ensuring is broadly-compatible (which should help prevent incompatibility waste when it does become ubiquitous).
Also, presently anyway, wireless charging generally has power limits on the order of 5 watts, while the USB 3 PD spec allows for up to 100. A modern mobile phone pulls more than 5 watts from a wall charger, so mandating wireless charging would also result in a short-term charging time increase. They're also not as easy to transport and use anywhere (e.g. on a train with a power socket but without a tray table). Many people would find that unacceptable.
My Nexus 5 had wireless charging, I had that phone for more than 3 years, and I never got to use it before it died and I upgraded to a 6P, which doesn't have it.