If the true cost of pollution were pushed into the sale price for end users, end users would have to reduce their purchases of non repairable items, and consumers would then value repairability as a feature, incentivizing manufacturers to cater to that.
It's much easier to force the change this way than through figuring out the correct wording in legislation, which is bound to have loopholes and be subject to costly (time wise) legal conflicts.
The root of the issue is that things are so cheap, repairing them makes no sense, regardless of repair-ability. Manufacturers didn't one day decide to drop repair-ability. One did it, and found that they were not punished by consumers. In fact, they were probably rewarded by offering new "features". Then another manufacturer did it, then another, and so on. And obviously, it works. I just went to someone's house who was showing off their fancy new fridge with a see through door.
Of course, the very very root of the issue is humanity's excess consumption which is causing harm to the environment we live in, but as I wrote earlier, that faces insurmountable political headwinds.
Manufacturers already pay $ proportional to the amount of fossil fuels spent, and this doesn't cause them to consider future consequences on the consumer. They still think vendor lock-in and planned obsolescence are to their advantage.