Questions around deploying to existing resources

[NMRS-TWalker]

I followed the below article to deploy an Aspire app to existing resources (e.g. group, container registry, etc.). I find it odd that you first must run provision and allow it to create all the required resources itself (and then delete them) before you can then deploy to your existing resources. Why can't we just specify the details of the resources in the .env file and then deploy? And why does Aspire not allow you to simply pick existing resources vs wanting to create new ones every time?
https://blazorhelpwebsite.com/ViewBlogPost/20069