I have a pair of PearlAcoustics Sibelius single driver Voigt tube speakers, and love them. If one argues that the audio signal can only be degraded by components, having no component such as crossover is the ideal situation.
I've also seen some old audio luminary quote (from B&W founder????) that ideally there is a single driver speaker, but if you cannot get a decent result, then add a second, if that is not decent then add a third. That means, multi driver speakers are the result of the inability of a speaker designer to make a good single driver speaker.
There is also the problem of wave cohesion from multiple drivers, that is non-existent with single driver models.
But as always, to each their own.