Cost

Like many conveniences in software development, a shared database is a tar pit waiting to fossilize a project. Developers overwrite each other’s changes. The changes I make on the server break the code on your development machine. Remote development is slow and difficult. Avoid using a shared database at all costs, as they ultimately waste time and help produce bugs.

You can manage scopes of time, cost, and quality much more effectively by basing your decisions on working software with actual feedback and metrics, not just task items on a project schedule.