In Australia it is law to include content and laundering/care labels on all textile items, particularly those that are to be worn or laundered. I worked in the fashion industry for years and have heard many stories of customers prosecuting designers/labels for incorrect or no labeling. One funny story was about a lady who purchased a 'flocked' skirt. The label for dry cleaning was incorrect, and when it was laundered, all the 'flocking' disappeared. She took the designer to court and won. Not sure what the outcome $$ was, but she stated it was an 'inconvenience'.
Sometimes it is difficult to label items, more so because the label destroys the aesthetics of the garment, particularly if it is reversible.