Auto creating community profile when a customer signs up for your product?

Just a few thoughts:

How would the user pick their username?
What if you decide to assign the username with their name on it and they dont want that?
How would they accept the Ts and Cs of the community?
Community profiles are public (unless your community is locked down). Do they approve of their profile being public with a username you choose for them?

I’ve thought about this too, but ultimately thought we’d end up with a bunch of unused profiles (if we figured out how to make it happen). 

For us, we use SSO and when we create the user, they get permissions for Academy, Community, Support … but they still have to create an account in the community.