US $3 Bills?

Okay, I have read a few things before about how, when the Treasury first started issuing our paper currency, there were plans for a $3 bill, so, I would like to know, why do you guys think these plans were dropped? I think it would have been neat if you could get $3 bills along with some $2 bills from the bank, as I know a $3 bill would circulate about as much as, if not less than the $2 bill circulates. I wish we could get the Treasury to resurrect those plans, even if just for a commemorative item and not made for general circulation. I did have people telling me that the horse track people would love a $3 bill, so that they could rause their minimum $2 bet to a $3 bet.

On another note, I can't believe I once read that Canada used to use $4 bills, and eventually switched to $5 bills in their place. Interesting.