Speaking from my own experience, but is it possible that the suicidal thoughts neural pathway has been worn so deep by repeatedly going down that thought pattern when you're depressed, that it just feels comfortable to go there, that it feels bad to let go of the suicidal narrative, like letting go of a treasured promise, a friend, that you're not used to thinking in terms of future or doing things you'll enjoy, that even though you're not feeling depressed your whole being has already given up on life entirely and just doesn't have the energy to switch tracks or doesn't know it can or should? That the suicidal narrative is just very loyal to you and is keeping its promise it made when you were depressed of giving you an out?