You may be right, I was speculating quite a bit. To be honest, I would be interested to know if some research has ever been made on the subject, i.e. roughly speaking "passion space configuration". I really don't know if the hypothetical "passion function" has some very localized peaks or is generally smooth (or has both large plateaus and sharp peaks!). The only evidence I have comes from myself and it points in both directions, i.e.:

a) I hate pretty much every sport involving coordination, except for tennis (sharp peak hypothesis)

b) I like pretty much every tabletop and card games, some more, some less, but with a small variation between them

The "plateau hypothesis" could explain no passion <= the level of the plateau is low. The "sharp peak hypothesis" could explain no passion <= you never reached the small region were the peak is situated.

Edit: found a better example for a)