In a group with N people, there are N² possible communication paths. As N grows, N² grows much faster, resulting in an unmanageable overhead in big companies.
However, in my experience, the overhead is actually worse than N² — worse than you having to coordinate with a number of people. That’s because you have to coordinate with some of them multiple times, because when you talk to someone, they don’t have the complete picture, or their view changes when someone else talks to them after you’ve talked to them. So you talk to them yet again.
Or you talk to person A, then B, then A and B together to resolve a disagreement. That’s again worse than N².
At some point you give up, and make an imperfect decision, which may lead to a suboptimal UX. Or to avoid communicating, which leads to silos, an us-against-them mentality, and so on.
In many ways, big companies suffer from a worse than N² communication overhead.