A contract problem becomes a lawsuit, which becomes a judgment, which becomes a collection fight, which becomes an appeal. A lawyer needs the whole map.
Legal problems do not respect practice-area boundaries. The law is a seamless web, and a matter that starts in one corner of it often ends in another.
A lawyer without the full baseline misses things — the collection consequence of a judgment, the appellate issue buried in a trial ruling. We practice across the web because the matters do too.