The United States/Canada don't have a "loser pays" rule, so this exposes me to legal fees.

Right now, any lawsuit against me can be dismissed on summary judgement because even if my software causes harm, that's not a legal wrong to the extent I've disclaimed liability.

If you adopt any fact-specific standard for liability, that needs to be adjudicated in a trial. The legal fees alone would surpass the actual liability.

That creates huge leverage for the party with more resources. That kills hobbyist open-source development, since if your project takes off but a large enterprise finds it defective, they can threaten to sue you to enforce the "warranty" you were required to give.