I used digital crop much before than I started used 35mm film. Still 35mm equivalence is meaningful as it tells me what to expect. For example if a camera with a given crop factor has a "24mm lens in 35mm equivalence" that is much more meaningful and easy to understand than saying "12mm lens on a 4/3 sensor" or "16mm equivalent in APS-C 1.5x" or "14.5mm equivalence for 1.6x APS-C" or "4.3 mm on a 1/2.33'' sensor". It's sort of an informal standard when so many sensor sizes are available.