God accepts the devotee's simple offering not for His need, but to establish the devotee's eternal relationship through love.Listen — Srila Prabhupada Uvaca
Prabhupāda: patraṃ puṣpaṃ phalaṃ toyaṃ yo me bhaktyā prayacchati tad ahaṃ bhakty-upahṛtam aśnāmi prayatātmanaḥ [Bg 9.26] [If one offers Me with love and devotion a leaf, a flower, fruit or water, I will accept it.] Now, the Lord Kṛṣṇa says that "Anyone who offers Me in devotion these four things," patraṃ puṣpaṃ phalaṃ toyam, "a bit of leaf and a bit of flower, a little fruit, a little water..." So He is pleased to take, accept. Why? Because we are offering Him with devotion and love. That is the only way.
Just like if you offer me varieties of foodstuff and very palatable dishes, but if I am not hungry, then all these palatable dishes and varieties of foodstuff is useless. I cannot accept anything. Similarly, if you offer anything to the Supreme Lord, He is full; He does not require your offering. He is always being served by hundreds and thousands of goddess of fortune.
Lakṣmī-sahasra-śata-sambhrama-sevyamānam [Bs 5.29]. [I worship Govinda, the primeval Lord, the first progenitor who is tending the cows, yielding all desire, in abodes built with spiritual gems, surrounded by millions of purpose trees, always served with great reverence and affection by hundreds of thousands of lakṣmīs or gopīs.] We are, in the material world, we are seeking the favor of goddess of fortune, but in the spiritual world, hundreds and thousands of the goddess of fortunes, they are eagerly trying to serve the Supreme Lord. So He is full. He has nothing to accept from you.
But He likes that you should offer Him something. Just like a rich father: He does not like any help from the son, but if the son, after he is grown up, he is earning, and if he offers something to the father, oh, he becomes very happy. This is natural. So our connection with the supreme father is like that. He is not in want.
He does not require anything from me. But it is for my interest. If I offer something, then I become a very pet son of my father. This is called bhakti.
This is devotional service, or Kṛṣṇa consciousness. And why should we not offer? Then we are ingratitude. Suppose the father is supplying everything, and if I do not offer anything to my father, is it very good business?
No. So here the ultimate, even the poorest of the poorest, he can offer these four things. Otherwise if you have got means, oh, you should prepare very nice foodstuff for the Lord. At Vṛndāvana in India there are temples still, they are spending thousands and thousands of rupees for palatable foodstuff, offering to the Deity. And those foodstuff are distributed to the, I mean to say, the devotees.