Compartmentalizing workers from each other and from customers is a means of control. Specifically management is trying to make sure that their developers do not get exposure to internal or external groups that may try to hire them away. Or give them a job if they get fired or laid off.

Consider

Case A: Customer knows you well understands you are competent. If you want to leave or are laid off that customer might eityher hire you or know someone who does. Or at least will give you a solid reference.

Compare with.

Case B: Customers and others only know you through your boss.