The Guardian article references Which? magazine
Airlines including British Airways and Virgin Atlantic have resisted calls to remove “no-show” clauses, which bump passengers off the second half of a return trip, despite heavy criticism from regulators and calls for a ban.
Consumer body Which? wrote to nine airlines in December, warning they may be breaking consumer laws by keeping clauses that cancel the second leg of a return flight if a passenger misses the first leg of the same booking, forcing some customers to pay hundreds of pounds for replacement flights. In many cases airlines can sell on the same tickets, doubling their earnings for one seat.
Of the nine airlines, only Flybe told Which? it would change the clauses, although it has not removed them completely. The airlines that retained the clauses were British Airways, Virgin Atlantic, Emirates, KLM, Air France, Singapore, Qatar and Swiss.
I am not surprised as this earns them money. If people want 'headline' prices that are low - then the money will come from somewhere else.