I never quite got that rule either. When a player lunges in with a bad challenge in a domestic match his team mates will usually surround the offender aggressively (well, I say aggressively, for a footballer that's more likely 'handbags' with a pathetic shove in the chest), and they will likely be all over the ref demanding something is done about the challenge. Waving an imaginary card in the air - wasn't it something that began in world cups when foreign players simply couldn't speak the same language as the ref? In which case I never really saw what the difference was. We do it ourselves in the crowd too, with our chants of 'off, off, off' don't we?