Across an enormous range of Indian sweets, the flavouring reduces to a small set: cardamom, saffron, rose and nuts. That narrowness is functional rather than a limit of imagination.
Why dairy sets the constraint
Most Indian sweets are built on milk, cream or fresh cheese, and dairy is a demanding base. It is rich, mildly sweet already, and it mutes anything sharp.
Flavourings that work must be strong enough to register against that richness without introducing acidity, which would risk splitting the milk.
That rules out most fruit and all citrus in the traditional repertoire, and it explains why the surviving flavourings are all aromatic rather than sour.
What cardamom brings chemically
Green cardamom holds a volatile oil dominated by compounds that read as sweet, camphorous and faintly citric at once. It reaches across dairy without competing with it.
Those compounds are fat-soluble, so they disperse through milk and ghee thoroughly rather than sitting in one part of the mixture.
Grinding releases them immediately, which is why cardamom is crushed at the point of use and added at the end of cooking rather than the start.
Why saffron works despite the quantity
Saffron delivers colour and aroma from a very small amount, and both its pigment and its aromatic compounds are readily extracted into warm liquid.
Steeping the threads in warm milk before adding them draws out both, which is why recipes specify that step rather than adding the threads directly.
Its flavour is faintly bitter and hay-like, and against sweet dairy that slight bitterness prevents the result from tasting flat.
How nuts function beyond garnish
Ground almonds, cashews and pistachios thicken as well as flavour, contributing body without any starch and without diluting the dairy character.
Their own fat carries the aromatic compounds from the spices, so a nut-thickened sweet holds cardamom and saffron more persistently than a plain milk one.
Whole or slivered on top they also supply texture, which a soft milk sweet otherwise lacks entirely.
Why rose and screwpine sit alongside
Floral distillates are used in small quantity and mainly in syrups and cooling preparations, where a light aromatic lift suits the dish better than a heavy one.
They are volatile enough that they are added off the heat, since a few minutes of boiling removes most of what makes them worth adding.
Their use also varies regionally more than cardamom does, which is one of the clearer ways to place a sweet by its origin from taste alone.