Is I-134 mandatory for B2 visa

Is I-134 required for B2 visa for my parents (dad & mom)? I heard it was not necessary but, was for spouse VISA

If your parents are self sponsoring their visit including their expenses during the stay and financially independent , you may not file I-134. In this caae they will need to carry supporting financial documents and be able to prove the ability to self sponsor their US trip.