When your system is set to not automatically create a Account, Contact, and Opportunity upon lead qualification, the system does not enforce the BPF required fields in the Qualify a Lead section. This means that if certain fields are not required on the form to save a record, but is a required field for qualification and say account record creation (Example field- Account Name), then the system does not enforce the BPF. If you tell the system you want to create an account, it will not due to the required Account fields not being filled on the lead.

In other words, turning off the Automatic record creation during the qualification process makes the BPF useless.