Earlier quoted context omitted.
They don't "disguise" things as burgers, sausages etc. That's how meat has been prepared since time immemorial across all cultures. Why do vegans and vegetarians insist on disguising vegetables as meat - now that's the question. Even though the same cultures have a mind-boggling variety of foods that don't involve meat, and don't pretend to be meat.
Those are not the natural forms of any animal's meat any more than they are the natural forms of vegetables. What you actually seem to be saying is "How dare vegetarians prepare their food in similar ways to how I do?" The idea that vegans are being sneaky with their foods is kind of funny considering the usual reputation of vegans is best captured in the joke "How do you know if someone is a vegan? Don't worry, they…
Ah yes. The non-natural form of "vegetables that taste like pork hamburger". Funnily how you never see meat producst disguised or sold as replicas of non-meat products.