Point isn't buying yet another charger, but reusing one you get with assorted devices. Otherwise we aren't cutting on waste but creating even more. Sure, mouse charger was a bit of a caricature just to get to point, but eg. if I buy tablet, laptop and a phone, I'll probably get 3 chargers which I can then just use for example one in office, one at home, one for emergencies/travel, instead carrying all 3 with me. So if lowest they'd be allowed to pack is 5W that'd be pretty useless even for that "emergency" use. But if I get 25W (phone), 60W (tablet) and 100W (laptop) then that slowest 25W is still kind of ok for emergencies, and sure enough as we already knew those 60W/100W will easily charge anything from 0.1W to 100W. I'll go back to that mouse, sure, you've never seen anyone pack a charger because they're saving money and on a 20$ mouse adding 10$ charger would be dumb so they add that joke of 15cm cable at best that costs pennies. And trust me, those phones that currently charge with micro USB won't rush to pack a 60W charger, they'll pinch pennies and pack lowest they are legally allowed. So if lowest that PD 3.0 allows is 15W - that's exactly what we will get.
As for asking questions and then wanting different answer,
@TheLostSwede , my only fault is not being clear enough resulting in you not understanding question in the first (second or third) place. I have asked 3x what is the minimum allowed spec. I'm unsure how is that hard to grasp. I didn't ask what's the lowest current it can provide, I can read just about everywhere that PD negotiates and varies in small 30mA & mV steps, but I did not ask that. When I ask what's lowest legal speed of a car on a highway you don't answer that car can go 0-100km/h. There is a legal MINIMUM in some countries and you aren't allowed to drive a tractor at 5km/h on highway, you need to go 60km/h at least. Same way I wanted to know lowest "legal" (in-spec) wattage that charger must provide for it to be called USB PD 3.0 certified. And so far answer looks to be - "same as PD 2.0 which starts at 15W".
Quotes I gave were historical as I bolded word MANDATED just for your eyes, so you can see that USB 1.1 at first MANDATED 2.5W, then USB 3.0 brought that to 5W, and finally PD 2.0 brought that to 15W. PD 3.0 did not change that so no quote, yet PD 2.0 isn't obsolete or deprecated because PD 3.0 builds on it.
Btw this was my source:
But hey, if they were wrong so am I. I guess I should now get my evening reading, they say it's "just" 410 pages of USB specs... It might be easy to get lost in translation when original work is 410 pages of specs.