Summarized from https://discuss.circleci.com/t/organization-wide-webhooks/2200 :
Currently we are setting the same webhook for many projects. It would be handy to have an option for organization-wide webhooks, that is, webhook notifications that apply to every project of the organization.
As an example we currently set the exact same Slack hook for every project, and it is very easy to forget doing that when adding new projects. GitHub introduced the exact same feature a while ago and it’s been an incredible help for us.