searay,maybe a couple of reasons or all of them
1:Undisciplined
2:Not 100% confident in your ratings
3:If you can rate them so well and switch you have a pumpkin for a head.(No offence meant,as Ken Howard used to say,"Off goes my head and on goes a pumpkin")
4:Easily swayed if something for some unknown reason seems better after you've done the hard work and yet it still does not qualify.
5: Mixing punting with imbibing in the demon drink.This happens quite frequently where discipline is lacking.
Good luck.