Oak-ord?
 

Looks like United has discontinued direct OAK-ORD service. That's a trip I make pretty frequently (family in Chicago). Only Chicago option from OAK now is WN to MDW, or a connection. Maybe there's an opportunity for JetBlue here?

B6 is having trouble getting landing slots at ORD (see the announcement re the new BOS service from today) so adding any service there is way more complicated than throwing a plane at a route. If UA cancelled it I'm guessing it was because they found something more profitable to do with the plane or the slots, not because it was making a lot of money for them. So it may be less convenient for you, but there are probably some real financial reasons behind it.