"Pet crazes": a purchasing fad initiated by popular on screen representations, and reinforced by badly researched photo-led tabloid journalism. Photogenic animals are labelled as the next "must-have" pet, trend-setting breeders are afforded free national publicity, and an unsuspecting public can make the "craze" a reality.
If you can keep your dog in sight at all time, be aware of what they are doing and be confident your dog will come back to you promptly when you call, then there is no need to put them on a lead. But if you can not be confident they will return when you call, then a lead is the safest option for everyone.
Bobi was a political pawn, used by the media to condemn the RSPCA. In this case, the two charities in question were both doing the right thing in relation to the remit of their policies. The media hysteria, public bias and negative publicity meant that the death of Bobi would have haunted the RSPCA in 2014.