free order settings marketpress

Dear,
marketpress free oder settings.
what is this and why is obbligatory?
I can imagine this is when the product is free?!
But then why if this is a free oder there is the indication to payment method?

From my point of view it would be better to eliminate the all free oder tab but maybe I don't understand for what is this.
Happy to read about your explanation.

Thanks & Happy New Year
Paddy