I was wondering, as we can create different environments in Launch like development, staging and production and it also exposes the corresponding url like <script src="//assets.adobedtm.com/launch-blahblah-development.min.js" async></script>. Why don't we just directly add this to the AEN's page header instead of going through all the cloud settings? Wouldn't this grant the devs and stakeholders more control of what launch config and environment they want to run, instead of getting locked to just using launch-staging and launch-prod?
You can absolutely do that - the integrations are there for ease of access. Some companies don't want to worry about the manual implementation of Launch, and would prefer using the UI to do it for them. Others, such as yourself, don't see the value of an automatic integration like that and would rather just plop the Launch embed code into their site's template manually.