TWR: Things have changed and moved on ...different methods, different materials, different ideas. For example, paintwork used to be solvent-based...now it is all water-based, even the clear top-coat. So, methods and materials used for car-cleaning have evolved.
Proper professional valeters (not those at the local supermarket!) never use washing-up liquid, sponges, brushes, chamois leathers etc. Better things are now available...if people want to get the best results.