Why? Quite a few reasons. Mainly I am attracted to simplicity. Plus I am lazy too. Only the simplest can reveal the most complex. There is no simpler speaker arrangement than open baffle. To me enclosure and crossover are unnecessary evil. No enclosure is best enclosure. As well as no crossover is best crossover.
Lowthers have been used in almost any possible arrangement. Large closed enclosure, bassreflex enclosure, mostly backloaded horn enclosure, Voight pipe, transmission line, front loaded horn and so on. I have been listening to Lowther on open baffle for more than ten years now. Finally there were other people putting Lowthers on open baffle, thanks to Dick Olsher and Bert Doppenberg. Lowthers sound on open baffle very transparent, fast and alive. Very much like live music. Side cancellation sharpens the sound beam thus preventing reflections from the nearby walls. High directionality brings clarity. Reflections from the walls, those reaching listener within first ten miliseconds after direct signal, are almost eliminated by open baffle arrangement. Sound radiated towards back of the baffle is no problem, when it reaches listener it is already delayed by a significant tens of the miliseconds and diffused enough. Actually, it is giving spaciousness to the music, a feeling of reverbation in the room without obscuring the original front signal.
Once you will hear a good open baffle speakers, like those from Audio Artistry or Genesis, you will never go back.