I'd like to save on the currency conversion fees.
I have a number of US clients paying me in USD, so I already have USD accounts to receive and store that income.
It feels a bit wasteful to convert those dollars to CAD (and incur a ~1.5% from my bank), in order to pay an AWS bill that was originally drafted in USD, and then converted to CAD by AWS (with an additional 1.5% fee charged by AWS).