It isn't, but it is the oldest browser that still has enough market share to be worth supporting (in some limited circumstances). We're not discussing IE5.5 because it has effectively zero users.
Some web developers out there are still supporting ActiveX components that no one is willing to replace. I don't think anyone would advocate building a new site using ActiveX though. At some point we have to move forward and adopt new technologies that improve the way things are built. We're at a point in web dev where Grid is ready for mainstream use.