The hankering after these originates from pride, error of judgement, and cupidity. The Brahmanas realise the presence of Vishnu in every sacrifice.
मानान्मोहाच्च लोभाच्च लौल्यमेतत्प्रकल्पितम्। विष्णुमेवाभिजानन्ति सर्वयज्ञेषु ब्राह्मणाः॥