For the most part, details would actually be required for purchases. Many payment providers for example would not allow use without address details. Then you have the setup of fraud integrations which would certainly require information before being used, otherwise there is no way in which to track details. You also have the situation internally of an admin being able to track through items. You could end up with 100 dummy guest transactions which would only really be able to be tracked by IP address or email if that is provided (and you are then already into asking for at least one item from the user).
These are just a few of the considerations. However we are community software at core. The intention of our software is to create community, and encourage registration of accounts into that community to promote content. Creating cart software for guests to be able to use without registering an account in any way would simply go against the intention of the software.