It transitioned people to using the same suite of products, which I think is huge for the creative industry at large; particularly with making it easier to transfer files from person to person for collaboration, delivery, etc.. Remember when some designers used Photoshop, some Fireworks, and some Corel Draw?

Fireworks was/ is for vector based graphics. That is a different use case from photoshop.

Fireworks a hybrid between vector and raster. It's for web/interface design, which has plenty of overlap with Photoshop.