The problem
A company with several products repeats the same work. Each product needs a sign-in, messages and permissions. Each team writes its own version. After one year, no one knows which version is correct.
The reasoning
We share a component at the second real need, never at the first. If you share too early, you guess what the other products need, and you guess wrong. If you share too late, you pay for the correction. The second need is the first moment when you know.
The effect
One correction helps every product. If a need concerns only one product, that need stays in that product.