The emissions from vehicles are different from plastics produced by factories.
Also, while important, 2-3% of world emissions is a drop in the bucket compared to the other 97%. Let's consider the other causes and how we can fix them.
Think about this: for many people, not driving to work is a big deal. If people collectively decide to do that, that's a lot of effort and inconvenience just for 2-3%.
There isn’t really a magic wand we can wave and get 50% back for free and without inconvenience. The other 97% involves things like individually figuring out where our electricity generation goes. Or figuring out which farms to shut down, or what manufacturing we don’t like anymore. All of this must happen. It will be inconvenient. I picked a slice that is immediately relevant to a lot of people here. But there are a lot of axes to look at this.
while 3% might sound like a drop in the bucket, there isn't any single specific chunk of the rest of the 97% that will immediately cut, say, 30-40% of emissions (also remember that 2-3% is the super specific "Americans not driving cars", not "everyone in the world not driving cars").