It's not made of plastic. That's "imitation leather", stuff like Naugahyde that has existed for decades. There are many new plant-based leathers that are exciting and interesting, including using the SCOBY from kombucha.

It's called vegan leather because it looks and acts like leather and takes the place of leather. It's a protein-based hard wearing impermeable fabric, it's fucking leather.

It's more leather than so-called "Genuine Leather" typically is.