As someone who builds and maintains cloud infrastructure, I have always been leery from a security perspective of giving third-party services, such as CI/CD platforms, access to resources. All the service vendors claim to take stringent precautions and implement foolproof processes, but still, vulnerabilities get exploited and errors happen. Therefore, my preference is to use tools that can be self-hosted. However, I may not always have a choice if the organization is already committed to an external partner, such as Bitbucket Pipelines or GitHub Actions. In that case, in order to apply some Terraform IaC or deploy to an autoscaling group, there is no choice but to furnish the external tool with an API secret key, right? Wrong! With the proliferation of OpenID Connect, it is possible to give third-party platforms token-based access that does not require secret keys.
The problem with a secret is that there is always a chance of it leaking out. The risk increases the more it is shared, which happens as employees leave and new ones join. One of them may disclose it intentionally or they may be the victim of phishing or a breach. When a secret is stored in an external system, that introduces an entire new set of potential leak vectors. Mitigating the risk involves periodically changing the credentials, which is a task that adds little perceptible value.