This is only my opinion, and I know not all agree with all of it, but my 2p's worth is:

1. Increasing costs and reducing track time
2. Riders getting older and retiring
3. Cost and hassle of the Mountain Course licence
4. Autocratic attitudes of some towards riders
5. Difficulty of winning a rep against current TT riders on superfast big-budget replica machines

To be honest, for all of the above reasons I retired in 2006, and I've been tempted back this year with the classic 750 class. However I will not be back again.

Doubtless this will please some who have no time for "Holiday Racers".