Because people who would have cancelled Amazon Prime over their politics would've done so a long time ago.
However, I have initiated closing my Amazon account. In this case Amazon is attacking our fundamental right to freedom of speech and freedom of association and our freedom to disagree with the government. The problem at this point it will take at least half of the 75 million who voted for Trump to shut off Amazon to impact them in any way. If we to not get tens of millions to respond Bezos could care less. I am doing the same with my apple account.