DX/DXi as a plugin format is basically a relic. I remember first reading about it as being advantageous because of how it leveraged DirectX and so it somehow "fit" better into the Windows architecture. The standard never really caught on in plugin market, not like VST, AU and AAX did. Not sure why, but it could have been because of certain complexities with installation/registering that overshadowed any technical advantage.
Anyway, as there is really no market for DX plugs, it really is a remarkable gift that these wrapper plugs even exist.