Another reason for all the additivies is to make nacho cheese melt and run like a thin sauce, in a way that cheese doesn't. But with normal cheese you get other desirable organoleptic qualities that can't be reproduce with additives.

For an example of the organoleptic qualities I'm talking about, watch this video:

https://youtu.be/4CVzqJWkodA?t=834

Look at how elastic the texture of that alpine style cheese is. Slices a few millimitres thick can be rolled into a cigar without breaking. That kind of texture cannot be reproduced artificially. And it can't be reproduced by "vegan" cheesemaking either. You need milk proteins for that and you need milk to be coagulated by rennet enzymes and the enzymes released by starter culture and ripening culture lactic acid bacteria while the cheese ages.