1) Companies are not incentivized to produce incompatible cables, the industry has done a remarkably good job of settling on basically a single standard, so the incentives seem to run counter to what you say. The major hold out introduced their own cable standard 2 years _before_ USB-C even existed, and even they were rumored to be moving to USB-C anyways. (I'm sure people will credit the law with this even if it had nothing to do with it.) Would it have been good if they had switched to USB-C earlier? Sure, but that would mean... people throwing out their old cables that worked perfectly fine.
2.) Would the amount of charging cables you have purchased in your lifetime even fill up one regular-sized (13 gallon-ish) trash bag? I don't know how many charging cables you are buying or what your uses are, but I'm struggling to see how it's a "staggering" amount of waste. I'm a somewhat avid electronic geek, I own multiple Raspberry Pis and other hobbyist electronics. No way would I even come close. When I do buy new cables, 90% of the time it's for reasons like the old ones have worn out, or I have a new device that needs to be permanently plugged in.
~~~Edited to add~~~ All my consumer electronics devices have stopped needing their own charger for years now. I use the same charger and swap out a cord.