Hard to say. I've known a lot of elderly people who were longing for death a long time before it came. Some of them would never have done it themselves though because they were religious and saw it as sinful.
That goes the same for anyone who believes- for whatever reason, that the act of it is wrong in some way. My Dad has alluded to having suicidal thoughts (unsurprisingly) after my Mum died but in part, he stayed alive for me. Partly why I'm returning the favour now.
It's not just cowardice that stops people from CTB. Sometimes they realise the collateral damage it would do to their loved ones so, they try to hang on for them. They may want to go but realise they need to stay.
It's hard to really know though. I think we almost see it as normal/ inevitable to have suicidal thoughts. I don't know that it is though. One colleague where I worked once responded to a radio announcement about suicide to say: 'I could never imagine feeling like that.' So, maybe to some people, it just never occurs. Others just seem to have it in the 'off limits' part of their brain.
Many people do see it as wrong though I believe so, maybe it's something they don't go too near to be tempted by. There must be other things like that in life. If we all did what we truly wanted and felt like we 'needed', wouldn't we be breaking the law all over the place? That doesn't mean we 'envy' criminals because they indulged in whatever it was that was forbidden. Do you envy someone their wealth when they defrauded lots of pensioners to get it, got caught and went to jail? No (hopefully not) because you can see the collateral damage on others and on them ultimately.
Some people even here may never CTB also because the prosect of failing an attempt with terrible injuries is too frightening. They may also be living relatively comfortable lives (practically speaking,) so- that may not be enough to push them into doing it.
Although I hate to agree with a pro-life statement, sometimes we likely do take suicide as 'the easy way out'. Not to say that it is easy of course. But still, it can quite often be because people's situations are dire or, about to turn that way that it pushes them to CTB. Suicide- even with it's risks probably seems 'easier' than living under such awful conditions. So- someone can be unhappy their entire long life but perhaps- if they aren't backed into that corner, they may never escape. Of course, if say Nembutal was freely available- I imagine that would change things.