Are you saying PG/YC is in the business of being charitable? I think that behavior only emerges when the average payout is larger than what they put in..
How do you explain YC investing in Non-profits like Watsi? There is more to YC than the payout. There is definitely a core goal to help good people build better products. Money just usually follows.
I don't follow. A donation is a net loss even after the tax deduction. There is no profit from funding a non-profit, even if you can take a tax write off.
If you want to be cynical, good PR would be a much better explanation than something involving taxes.