Was backward compatibility the main reason YAML kept these implicit conversions for so long, or was there a stronger usability argument originally?

For yaml in the context of Ansible, this was recently fixed a little while back in v2.19.

They got more strict about booleans. For those who need/want the old behavior, ALLOW_BROKEN_CONDITIONALS can be set in the ansible.cfg or `is truthy` can be used for python-like version, but it becomes explicit vs being implied.