At the same time, it's nice to be able to eat a variety of foods. Some people who are vegans primarily for ethical reasons rather than health or taste reasons may miss meat and/or cheese a lot (especially in the early stages). In this case, these products provide a substitute for the foods that they may remember and enjoy but no longer choose to eat.
I enjoy meat and veggie food but I draw the line at egg and milk substitutes. Real vegan cheese is appalling and no amount of processing can make up for it. "Soy" cheese that uses milk protein is much better... and there are a lot more simple vegetarians than radical-Shiite vegans. Nor is there always a bright line. I have heard good arguments over whether honey is or is not vegan.
Eating out is always going to be a compromise if you really care about what goes into your body. I would prefer to reserve it for when I am out of town or special occasions - but even then what is more special than actually taking the time to cook yourself?
From the food hacking perspective, it'd be cool if someone did the opposite: fake vegetables using meat. Making beef have the taste and texture of a carrot would be pretty impressive.