Some people do not ever watch or record live TV or use BBC player on any device. If that's the case they can inform TV licensing that they do not need a licence therefore. That is if their viewing habits are solely limited to on-demand non BBC content from other services, eg. ITVX, Netflix, etc.
However if they do watch or record live TV, regardless of channel, or use BBC player they are required to have a TV licence. If enforcement officers become aware they are watching or recording live TV or player, they could face being taken to court or a fine of up to £1,000. Their risk, their choice....