The schools would love to play each other but the scheduling does not make it easy. For example, UofL has its 8 game ACC schedule plus the annual UK game. That's 9 games that are inviolable and booked solid. And it opened with Auburn, Purdue and Alabama 3 out of the last 4 years (essentially ESPN arranged matchups) and opens with Notre Dame next season. And then it needs to schedule the remaining 2 games as home games for the revenue and with teams who can fit it on their schedule (which are usually lower level teams who play for the paycheck but often includes in-state schools like WKU and Murray).
UC also has its own scheduling commitments. If UC can work something out to take 1 of the 2 "open" slots that usually exist, then it might happen. But the schedules have to work for both schools, and UC might not be able to get a home game in return, at least not right away. It will happen at some point but probably not soon.
Most UofL fans would like to see it and those of us from the Cinti area particularly love the idea. But simple math and reality don't allow it with ease anymore. Agree that it would be awesome to play for the keg in a bowl game.