A team usually consist of more than one person. Let's say a writer, a coder and the artist. Bigger teams might have someone for sound and music, animation etc, while smaller ones will have work sectors overlap/multitask. As regrettable as it is losing a team member, others have put a lot of work into a project and I certainly believe scrapping a recognizable one is a hard thing to do.
Yes, they could start from scratch, or continue rather than rework, but that would invalidate the work of all the other team members when the game wasn't at a point where they can just create a second one and continue from where they stopped.