I have been doing robotics for 20 years, and the "trend" to adopt a distributed architecture was already popular 15 years ago. ROS just adopted and continued that trend. I think you are missing some important points:

- a large amount of data can be transferred asynchronously. Pub/Sub is a great pattern to achieve that; the cases when you need a synchronous interface are the minority.

- a robotic software has MANY components, you need an approach that incentivize decoupling and lousily-coupled interfaces.

- this lousily-coupled architecture has been a catalyst for innovation and cooperation, because it makes it easier for people to share their code as "building blocks" of a larger system.

Is there a considerable overhead? Sure! But it is much more complicated to write thread-safe code in a huge, monolithic application.