So I think another factor that hasn't been mentioned is that at a large company there is often an aversion to two things: breaking existing services and duplicating work that another team already "owns" (the second part is normally done in vain, but still wastes time, as you can see by Google's message app mess). This results in slower agility already, because if someone would like to add a new feature, there needs to be some degree of communication with owners of the needed projects and coordination across teams. All of this takes time away from producing tangible work. The reason that this continues is because at most large companies (at least tech megacorps) this inefficiency is a rounding error compared to the boatloads of money that the company rakes in. The system in place keeps the ship moving and delivers innovation at a manageable pace, and as a result nothing in the organization structure really changes because the company continues to profit, and everyone internally reaches their objectives:

- Upper management: company is making money

- Middle management: engineers are doing work, projects are coordinated

- Engineers: projects move slowly, but getting paid and promoted and gaining experience

None of these objectives are "streamlining organizational structure"