I do think there's a massive underestimation of the human desire to live to be honest. Most people, most of the time want to live even when the quality of life is, to someone on the outside very very poor.
They might want to spend more time with the people they love, they might be scared of the unknown, but also it's one of our most basic and strongest instincts.
When someone really wants to die, and they can express that clearly and consistently over time after all palliative and psychological measures that are available have been offered and haven't changed their mind, then I think we can believe them.
I do think quite a bit of the time people aren't heard and aren't believed because we don't want them to die. Either because we love them and can't bear to lose them, or it's seen as failure of our care.
As things stand, people with terminal illnesses can refuse interventions that might give them a bit longer. We respect that they have that right to decide they've had enough, even if their family is distraught and desperate for them to continue. Do we think that some people are coerced into refusing treatment for financial gain? If so, what are we doing about it?