Why is our health system so interventionalist in dealing with the severely disabled?

I work in a hospital, and every day I see huge amounts of time, effort, and money being spent on invasive intervention for severely disabled people. Things like massive spinal surgery to give the lungs a little more room, making breathing a little easier. Often the patients who require this level of intervention are so intellectually impaired that, while they would feel less pain, would have no memory or insight as to whether their life is better or worse. Whatever slight improvement can be gained through intervention, their quality of life is still rubbish.

Although no one has the ability or right to actively deny a patient treatment based on assumptions regarding their quality of life, I often find myself wondering why we bother. Why not put them on palliative-esque measures, and just make their life a little easier without actually trying to correct their illness?

Please note I am interested in the moral issue here, not the logistical issue.