Great questions..And maybe Ben's father did see his wife at some point, but if that's the case it's either a side thing the producers don't find all interesting to explore..or that they are saving it for later fb's. So far we only had a single Benjamin Linus episode, more information is bound to follow I think.
Another either/or theory more plausible is that, either Ben's father was not that well attuned with the island to have such an apparition, or that he was too drunk half to make sense of it, even if he had a few.
OR, the memory of his wife was blocked and repressed (something leading to his hate for Ben and abuse of alcohol) that he wouldn't be able to 'call' it. OR, Ben's mother was upset with guilt projections of her husband onto her son (Ben), that no connection was made between the father and the dead mother. Though it'd be more fitting to see her as some angry ghost chasing her husband for tormenting Ben
