why do we prefer x-band for microwave waveguides?

Why do microwave wave guides operate in X-band frequencies? why not in K-band, L-band and in other bands?

Rectangular Waveguide Dimensions - Microwave Encyclopedia - Microwaves101.com

The question is wrongly posed. Waveguides can be and are used for any wavelength from ~50 cm ( ~600) MHz upwards to mm-waves and submillimeter waves; the advantage is a very low loss.

Other guide lines like coaxial and stripline are also used but generally have a larger loss.

There are also "overmode" waveguides with a cross-section measured in tens of wavelengths. Such waveguides are called beam-guides and can be seen as feeders of large satellite-communication antennas (chimney-pipes). The reason is even lower loss, very important for transmitting large power or for very low-noise receivers.

The X-band is particularly used for radars, terrestrial as well as airborne. Waveguides offer a low loss, so the microwave power generated in radar transmitter is not reduced on its way to antenna; also weak returns are not attenuated on their way to the receiver.

Thank you very much. I have been searching from a long time for this answer. Thanks a lot. :)