befree - it's all down to the issue of whether tickets sold are refundable or not and thus when the ticket is recognisable as revenue under accounting policies, and as to what data shareholders would really care about (number of people on each flight will be reported separately to the various aviation authorities under a different metric).
Remember that Ryanair would like it if customers who bought tickets did not fly - it means they keep both the base fare, and also because their policies make it extremely diffiicult to claim back the Govt tax, they in practice usually end up keeping the tax as well. A large network carrier like Air France is in a different position - it sells many refundable tickets to large companies - if one of their staff misses the flight, the company can easily just claim the refund including the tax.
There has been much debate on this forum over the last year or two as to how one compares "number of non refundable tickets sold" as given by Ryanair to "number of people / RPK flown" as provided by most network carriers, and thus how one can compare the performance of Ryanair to (for example) Lufthansa.