Because they are so high in umami! Besides the umami/savory flavor, dried mushrooms have that chewy texture that resembles meat more closely than any other whole plant-based food (except yuba, maybe). There's a reason why Buddhists following ahimsa (non-violence) principles have been using dried mushrooms to replace meat for centuries. The Buddhist cuisine came up with some of the best meat analogs throughout all this time and the usage of mushrooms is no exception.