Because there is an inevitable translation step between "customer wants X" and "engineers have to build Y to achieve X". This takes time and is a non-trivial task. I'm an engineer myself and I'm glad there are people between me and the customers. They're there to shield engineers from unnecessary tasks and scope creep. They are the necessary abstraction layer between engineering and business.

Ngl often times I wish there was a people person between me and clients. These damn people with their people things, ugh.

They probably wouldn't need a secretary though heh.