Specifically addressing WMA, which is a Microsoft creation, it is the only music player not supporting it, and it is the format preferred by competitive music stores. Apple’s response is that it opted to develop its own format rather than being forced to license from Microsoft.
Perhaps the solution is to force an open-source format for DRM, if that is at all possible. A standards body could be established to certify devices and software as complying with the standard. There are various good examples of such bodies in the computing industry.
Is Apple engaging in monopolistic practices by locking iTunes, its purchased content, and your music player together with no alternative options?