We have seen before how confusing USB-C can be: what cables and device support what capabilities. This article has more examples of confusion about the standard:
If you buy a USB-C charger that doesn’t support Power Delivery and try to use it with a Microsoft Surface, for example, the laptop will complain that it’s “not charging” despite receiving some power. Fixing this requires figuring out whether or not it’s the cable or wall charger that doesn’t support Power Delivery, and replacing it with something that does support it. There would be no way for a layperson to hold two USB-C chargers and know the difference between one that supports Power Delivery and one that doesn’t.
Furthering the confusion, some devices actually can’t be charged with chargers supporting Power Delivery, despite sporting a USB-C port — because they weren’t designed to negotiate the higher wattage being delivered by the Power Delivery standard. A pair of cheap Anker headphones I own, for example, refuse to charge when plugged into a MacBook charger. Other devices, like the Nintendo Switch, only partially support the standard, and some unsupported chargers have bricked devices, reportedly due to the Switch’s maximum voltage being exceeded.
If you need to use different ‘supported’ chargers and cables with different devices, how is that any better than a proprietary standard?