They are designed for all-day door, drawer or molding operations. They are production animals. Although capable of experimental work, shapers are usually set up for routine big jobs of long duration. Router tables are welter weights by comparison. It takes two routers to equal one shaper.
Router tables give up production for versatility.
In my view, the router table not only performs edge, face, and end cuttings. In addition, inside work is also possible. Dados, mortises, and other blind inside excavations are not possible with shapers, nor are dovetails, a distinct advantage for the router table. Router bits for all sorts of woodworking are common and there are probably more router bits than shaper cutters except for door, drawer and window applications. The router is an offshoot of the shaper, not a substitute for one.