Comment by seanmcdirmid

Merging later encourages better utilization of road capacity and eliminates bottlenecks further away from the overloaded resource. It's quite simple really, in this case the polite behavior is wrong, and if everyone would just be greedy, the behavior would no longer be impolite and would be more optimal (source, I live in china, this really works better than the alternative, we have plenty of overloaded resources).