Official response is oversubscribed and existing riders chosen on lap speeds.  I seriously hope no-one goes slower than 99mph in the F1 this year or breaks down.  I got screwed in the Supertwin class as the only race I did on it was the weather hit 2013 race in which I was 7mph down on practice times.  Sometimes you just don't fit the criteria.  I think I'll have to start wearing dresses full time and call myself Antonia Michelle and get in on the "diversity" criteria :-)