My need, and that of people all over the Home Counties, for singles is
very limited, two tickets so far this year. A one-day travel card (with
a Network Card) is only £1.65 more than a day return to King's Cross and
a Saver return to Zones 1 & 2 £1.20 more than a Saver to King's Cross.
So prepay isn't usable for millions of such travellers.

And it is not supposed to be. It is for Londonders not "people all over the
Home counties"