"Why aren't the designers and engineers sitting together?"

A good practice! Back in the day, Eric Carlson put his engineers, software folk, designers on the same floor of the same building. The idea was, communication depended on unobstructed access! In the same cube, ten times a day. Adjoining cubes - once a day. Down the hall? Once a week.

All that was superior to out-of-sight which meant you only communicated indirectly and infrequently. Anything is better than that.