A bridge needs healthy teeth to support it. Before it can be installed, the abutment teeth have to be reshaped so that the bridge slips over, like a crown. If teeth are healthy, this permanently and unnecessarily alters their structure.
Additionally, bridges may not last for more than a decade or so. They will ultimately need to be replaced with a new one. At a certain point, the supporting teeth may be too weak to hold a new bridge, due to lack of stability.