Everyone has their limit of what they can take, and a stranger peering in has no idea how much effort that individual has exhausted to get to this point. Accusations of laziness are meant to disparage and demonise suicidal people, creating a false narrative that if only that person had "tried harder and gotten the help they need" they would be cured in the swish of a magic wand.
Unwillingness to admit that there is no help out there for many issues lies at the crux of the just world fallacy. People want to believe that there is no sense of determinism or luck involved when calculating the trajectory of one's life. Is is far more soothing, satisfying, and comforting to think that we have control over everything and our decisions will always have a tangible impact on our life outcomes.
It would be as simple as acknowledging that a treatment for x condition hasn't been found yet, or that there are issues with our cultural and socioeconomic expectations that need to be addressed lest more people are driven to despair and suicide, but most people cannot do this. They cannot put themselves in the driver's seat when it comes to the road map of your life experiences, your mind, every trial and tribulation you've went through to reach this point. It is unfathomable to them that this one specific problem may not have a solution.
Others have already mentioned that there is a deep seated cultural lust for persistence and perseverance, despite a positive outcome never being guaranteed. I notice often in scientific literature that "lack of resilience" is often noted as the etiology of what clinicians and researchers label as antisocial or "depressive" behaviour. Language like that shows a distinct lack of insight into the amount of bullshit someone has to endure before they reach the point of no return. Hardly any of the people purporting such a bold claim will have their fortitude tested in the cruel ways that their lab rats and patients are subjected to.
Onlookers whose only interaction with suicidality boils down to social media campaigns and cheesy charity slogans have no idea how nonexistent "help" actually is in this world. They have a clear pipeline in their head of, this person is depressed! They need SSRIs and therapy, and when those don't work, you have to keep repeating these failed interventions over and over again in an act of irrational insanity, because eventually you will find that golden ticket.
Nevermind if you aren't depressed, we are going to shove you in this box and if you insist it isn't so, you will be labeled a quitter who doesn't want to put in the work or is in denial of what your problem is. There's an abundance of circular reasoning where others purport that you must be not seeking assistance of you're suicidal, and if you're still suicidal afterwards, you must not have sought enough assistance. It is utterly ridiculous.
Even if you do exhaust all options, they will repeat these same accusations like a trained parrot. Oh, you tried every medication out there and you still have PTSD? You tried over a dozen therapists, who were useless at best and mocked you for being autistic and having years of trauma due to abuse? You have physical conditions which aren't understood by modern medicine and can hastily be labeled as somatoform? You have no family and no one to rely on? Well sweatie, you just didn't try hard enough! You're so young, it'll work out!
I have actually still had these things said to me even though I have went through the wringer of failed "help" which leaves lasting damage. No one actually wants to try and understand what would improve someone's quality of life, or have respect for a decision that they are forced to make due to a logical thought process of wanting to escape insurmountable problems. No, they want to proselytise about moral failure/lack of willpower and persistence, while claiming that only professionals can understand your pain, professionals who are usually just as clueless as they are.
It really is an exercise of futility to try and find understanding with people who are unwilling to see suicidal individuals as anything but a downtrodden, unmotivated, caricature. Fuck it, there's nothing but more pain to be had when dealing with sentiment like that.
