Don't know why, only a guess.  My guess is that JB is not giving away enough of the store to suit anyone so far.  That being said, you have to firmly establish your negotiating position to engage those with a genuine interest and 'ability' (if there are any).  I honestly think that Briscoe's knowledge of what is behind door number 3 compels him to follow a particular path.  It is not implausible that having held out for two or three years could mean multiples in the final return (if there is any).

Perhaps the only interst so far has been from those who are compulsively risk averse . . . . .