If I were a quadriplegic, I would have ended my life long ago....But that would require assistance.
If I were, say, a Christopher Reeve type quad, I'd think I would too. Get myself one of wheelchairs with a straw and blow myself off the nearest pier or to the nearest train tracks.
Of course, I'm not so I have no idea what I'd think. Maybe I'd stick it out, hoping some motivated scientist finds away to plug nerve cells back together. Maybe take some of the billions dedicated to AIDS research and transgender surgery and throw it my way.
But, yes, I can't imagine a worse quality of life. And the burden on my loved ones...