Reciprocal lattice is useful for very similar reasons that the
time-domain Fourier Transform is useful for signal analysis.
(look at a stereo equalizer, for example).
Scattering deals with wave-vectors and Fourier Transforms of the
potential at small ranges, and thus the reciprocal lattice plays
perfectly into these techniques.
It is very useful that the FT of a Bravais Lattice remains
a Bravais Lattice.