I think players see an opponent as a threat more than an opportunity. So if there is someone already made a bid, people tend not to make a bigger bid because they are afraid of losing money. How would they see it more as an opportunity to earn even more, which it actually is? ;-)
Hmm, I think you are right... Maybe I need to put more time between the pots so that each feel scarcer... I don't know, I think you have a good point. If someone has already bid, what is my incentive to bid, I know that someone with initiative is already betting. If I bet I'm probably just going to get outbid. Going to have to think about that...