Logs carry more than debug context.
Structured logging makes it easy to include full context in every log event. That is also what makes it easy to accidentally include sensitive fields — and those fields spread to every downstream tool.
cardNumber
Payment card data in Datadog
password
Credentials in Splunk
authorizationHeader
Bearer tokens in Application Insights
ssn
Identity data in Jira tickets
These fields appear in logs because structured logging makes it easy to log full context — not because developers are careless.