Because George Lucas said you can't. It's G-canon, which means in the SWU it's like the word of God being handed down to us mere mortals,regardless of whether you think said "God" is an idiot,genius or both.
No matter what the novel said, it's lesser canon than G-canon and is trumped by what Lucas and Chee say. You can disagree and choose to believe something else in your personal perception of the SWU but the fact remains G-canon offically says it can't be done.
I understand that.
I guess I'm not arguing with canon so much as wondering out-loud if perhaps Luke used something similar to Revan. You don't think so? He obviously loved Mara Jade. So what do you make of that?