It doesn't have to be entirely - if any one bottleneck breaks the communication and collaboration (not enough seniors to review? Weird deploy process? Too few/b

It doesn't have to be entirely - if any one bottleneck breaks the communication and collaboration (not enough seniors to review? Weird deploy process? Too few/bad pms?) then people tend to reach for these kinds of structures. It honestly takes a lot of trust AND discipline from the higher up folks to let dev teams work in the self organized, effectively ad hoc ways described in these other comments.