Let me state right up front that I have ALS!
It's not 100% about how deeply you want to live, obviously, or there would be many more survivors. That being said, you can find a certain amount of people with ALS that live longer because of their attitude.
Stephen Hawkings made use of every technology available. He breathes through a trach and receives nourishment through a feeding tube. If everyone with ALS had these procedures there would be a lot more of us around. Most pALS (people with ALS) still decide not to have a trach installed. Why? Don't want to live disabled, don't want to burden their familes......
I think a big part of the dialogue is our collective negative feelings about being disabled. Stephen Hawkings didn't think like that (he's brilliant) and that's why he's alive today.