Additionally, a lot of vegns are also extremely health conscious, and so they tend to avoid a lot of unnecessary fat in their diet. A lot of chefs will say "fat is flavor," which is true, but what's also true is that fat conveys flavor. It sticks to surfaces in places that water doesn't and allows flavors to linger.
It's why the Impossible and Beyond Burgers are succeeding: they haven't lost sight of what makes a burger, a burger.