In the good old days just about all speakers had these controls. That was before we leaned to design our crossovers properly.
I find a type of tone control to be indispensable. This can be done at the speaker, or ideally, in a proper DSP full active crossover system, or at least a high quality digital studio DSP equalizer between the pre-amp and amplifier.
But most people will never do those last two things, and the built in treble controls on say the typical receiver are far from ideal. In addition, to effect a a proper tweeter attenuation slope requires knowledge of the speaker's actual inherent response curve.
Tannoy by the way have made the finest coaxial speakers since the 1950s. The Tannoy Monitor Golds have always been among the finest drivers available for over fifty years.
My view on co-axials; I have yet to see them pulled off without severe compromises. The Tannoys measure well(in context), only when you consider the insane topology they use: large cone mid bass drivers with a tweeter loaded in the center. But utlimately, they measure poorly overall when compared to very good standard layout speakers such as a B&W 802D. One very obvious problem is the degree of reflected/delayed energy as the upper mid and treble bands radiate from the relatively deep mid-bass cone area - the effects upon frequency response and final direct to listener CSD are substantially negative.
Stereophile measured the high end Tannoy Church Hill and one of the Tannoy Dimension models. The off axis response decreased very rapidly on both models in the treble band, as would be expected with this particular design.
Theile co-axials seem to measure better overall, considering both off axis response and reflections showing up in the CSD. But yet, Theile speakers do not seem to have cabinets built as well as the Tannoys, at least when you consider cabinet panel resonance.
-Chris