Why would they want to lose penny stock trading revenue? There is no reason they would. Rather, they are being pushed around by one of the few MM games in town. I'm sure there is a ton of complexity in their various contracts that none of us will ever know, but there is no way IB mgmt. suddenly woke up one day and decided they had no interest in collecting commission for transmitting orders.
Also, it might interest you that in many of these names, what you erroneously call an "odd lot" -- say, 2,000 shares -- can easily be 20% of the ADV. That's what makes this policy so absurd.
Taking a shot in the dark on this but
1 these are otcbb stocks. Who else is making a market - hence they need to adhere to what the market makers are demanding
2 FINRA hates otcbb stocks and brokers have unrealistic regulatory costs dealing with their questions and record keeping requirements - hence they May not be worth the trouble to offer them