You're right in some regard and I get where you're coming from. Many of us don't know each other, we haven't lived each others lives. We can talk and share stories, but we can never truly understand another person completely. Who are we to judge someone else's feelings and circumstances and take them through the same rigmarole they've been running around for god knows how long?
One thing we all relate to here is the feeling of being beaten down by life time and time again. The overbearing and dreadful feeling of having no hope for escape other than taking the final step of all. Most all of us here know how shitty, crushing, powerless, agonizing, consuming, draining, and lonely it feels. The comfort words bring varies from person to person, for some they mean nothing, for some they mean everything. Just being seen and heard is enough to get some people enough peace to enjoy their day. There's only so much we can do through a screen, but we want to tell them they aren't wrong for how they feel, they aren't alone. We tell them what we wish we could hear. If it may alleviate some of that weight even just a little, it might be worth it, there's nothing to lose by saying it. Another harsh fact is, there is nothing to say in certain situations. We're just as helpless as the people on the edge. The only thing we can do is try to alleviate the stress they're feeling so they can have one last moment where they can feel like they finally made the right decision.
I absolutely get the way you feel there's some ulterior motive behind every move, really, I do. I've been manipulated and gamed enough to know not to trust anyone no matter how flowery their words. To know that no matter what you say, they just won't really 'get it'. You're valid in the way you feel, and right for it too, don't put yourself down for being fucked over in the past. Idk, all we can do is hope to be of help in our lives, to bring some sense of peace for others or ourselves so our existences don't feel in vain. I just know I don't wish this feeling of apathy and hopelessness upon even my worst enemy.