Why demigod worship is recommended – and why it is unnecessary

This worship of demigods by the general populace is also advised in the Vedic literature just so people can accept the superior power of the Lord. The demigods are servants of the Lord deputed to look after the management of various activities of universal affairs. Therefore it is advised in the Vedic scriptures that one should perform yajnas to appease the demigods. But one who is devoted to the Supreme Lord has no need to appease the demigods. Worship of the demigods by common people is an arrangement for acknowledging the supremacy of the Supreme Lord, but it is not necessary. Such appeasement is generally recommended for material gains only.
Srimad Bhagavatam 3.2.32 purport