From time to time I get asked this question. I've got 4 answers, all true in their own way.
1) I got involved with Hep C treatment by accident. A single patient asked for help, said he was doing it with me or without my help so I figured he'd be better of if I helped. After that stuff happened and by the time I had second thoughts and looked over my shoulder it looked like the road behind was on fire and the bridges burning so forward looked better
2) Morally it really offends me that we've invented a cure for X and patients with needs-X can't get it because it's too expensive. I'm a simple soul. If I find somebody who needs-X I prescribe X and want them to get X - that's what I signed up for
3) I was a bit of an edge case as a kid. I fitted in because I was good at sport, not so much the people stuff. Seeing so many doctors put their personal interests (take no risks) before patient interests (already running the very real risks) made me sad. Supporting generics when most other doctors were too scared to fitted with a lifetime of always being on the outer.
4) I fly hang gliders and have done since 1981. It never ceases to amaze me that after 2000 years looking at the sky wishing we could fly very few people actually want to. Anyway, back in the 90's there was a brand called "No Fear" that had a slogan "If you're not living on the edge, you're taking up too much space" and I wrote this poem:
The Path We Choose
Do not shed a tear for me
For I would not for you
Instead just drink a beer for me
And know well that I knew
Dreams of flight do not come free
There comes attached a price
And we do not do it blindly
We know we roll the dice
Before you sail into the sky
A sky slow to forgive
Ask am I, afraid to die?
Or just afraid to live?
So if you try, to question why
When fate can seem unjust
We take these risks, not to escape life
But to stop life escaping us