When dealing with environments that should meet security regulations it is very unlikely that systems have direct access to the Internet: they connect to the Internet by the means of a content proxy.
When dealing with the need of access the online Ansible Galaxy, you may think that creating the access rule on the corporate proxy is enough to sort things out, but it isn't: besides the poor performances due to the latency for downloading contents from the Internet, there's also the security concern that it is possible to upload contents to Ansible Galaxy using that proxy.
If you are working in an environment with sensitive data, this is a huge security risk that you can mitigate by using an on premise repository manager that mirrors the contents you need from the online Ansible Galaxy.
This post shows you how easily you can mirror a subset of the collections hosted onto the online Ansible Galaxy by using Pulp3 with the Ansible plugin.