Rags, dippers and bigger London clubs have a larger supply of irregular supporters to shift excess tickets to. It's that simple.
Add in the facts that we've probably played at the new Wembley more than any club except Spurs, late announcement of dates and kick-off times and the fact that most people don't have an inexhaustible supply of cash, and it's easy to see why we don't always sell out. - It's easy for fans of other clubs to say they'd be up for 20-odd visits to Wembley in 15 years but it would be a different matter once they had to start paying for those trips. - It's also easy for armchair supporters and the media to snipe as they don't have to worry about the cost and availability of tickets, travel and refreshments.