The word modaka comes from the Sanskrit root mud (joy delight). The self is said to be the nature of existence (sat), consciousness (cit), bliss (ananda). One seeks bliss because one is of the nature of bliss. Nothing else will ultimately satisfy one that to experience that which one truly is.
Obtaining what one likes seemingly brings one joy. Thus Ganapati holds out the incentive and enticement of "giving one what one wants, so that ultimately one will want what he has to give." It is because one mistakenly looks for complete and lasting bliss in eternal things that one eventually becomes disappointed. Bliss is not "outside" but within. This should be self-evident with a little analysis. One and the same object does not provide one with the same quality or quantity of bliss at different times. Nor does it provide different individuals with the same bliss. If bliss were innate to an object, this should be the case. Further, it is because the fluctuations of the mind cease upon attaining one's desired goal that one feels a momentary joy. If one begins to long for piece of chocolate cake, one feels restless until that object is obtained. Mistakenly, one believes the joy that one feels upon putting that first piece of cake into one's mouth, comes from the cake. In reality, it comes from the quitening of the mind. No longer is the mind flickering, fluctuating flitting hither and yon demanding cake. The joy comes from this quitening of the mind and not from the seemingly simultaneous attainment of one's desired object.
How truly said!
The root of this analysis is of course the wonderful conversation in Brihadaranyaka Upanishad between Yagnavalkya and his wife, Maitreyi. I am quoting from the translation by Shri S. Radhakrishnan, II, 4-5, page 197:
Verily not for the sake of husband is the husband is the husband dear but a husband is dear for the sake of the Self. Verily not for the sake of the wife is the wife dear but the wife is dear for the sake of the Self. Verily not for the sake of the sons are the sons dear but the sons are dear for the sake of Self. Verily not for the sake of Brahminhood is brahminhood dear but brahminhood is dear for the sake of the Self. Verily not for the sake of kshatriyahood is kshyatriyahood is dear but kshatriyahood is dear for the sake of the Self. Verily not for the sake of worlds are the worlds dear but the worlds are dear for the sake of the Self. verily not for the sake of gods are the gods dear but the gods are dear for the sake of the Self. Verily not for the sake of the beings that the beings are dear but the beings are dear for the sake of the Self. Verily not for the sake of all is all dear but all is dear for the sake of the Self. Verily O Maitreyi, it the Self that should be seen, heard of, reflected on and meditated upon. Verily, by seeing of, by hearing of, by the thinking of, by the understanding of the Self, all this is known.
The first part in bold is quoted often in Raja Rao's Serpent and the Rope. Here is a link that gives the introduction to the principal upanishads by S.Radhakrishnan.