There is almost no market for the mono versions, and we don't even know if those tapes exist anymore (likely not). ... The unique mono tracks would have made nice bonus tracks, however.
Of course you're right, that's why I have finally managed to get the two radio station only mono albums and the UK mono release of Sounds Tijuana. With those three professionally dubbed, I basically have a pretty good collection of the original mono singles in excellent sound. Like many other's I've made my own "home brew" collection. I feel the vinyl used on those albums was better than what was used on the actual singles..