Because London Transport system is currently over crowded and near
breaking capacity point. To make London's omplyic bid a bit more
attractive especially as its losing points because of London's bad
public transport. If the omplyics comes to London then transport will
be free to everyone.
Letting people travel for free on an already overcrowded system. I
miss the logic? And also they want to make special "althelte only"
lanes on the road so they can beat the queues.