Vegetarian food across India varies so widely that dishes from two regions can share almost no ingredients. The divergence follows agriculture and climate rather than preference.
The staple grain sets the shape of the meal
Rice grows where water is plentiful, wheat where winters are cool and dry, and millets where rainfall is unreliable and soils are poor.
Each staple imposes a different meal structure, since rice needs a pourable accompaniment while a flatbread needs something thick enough to be picked up with it.
That single difference propagates outward into how sauces are made, how much liquid a dish carries and how many separate items appear on a plate.
Cooking fat follows what grows locally
Coconut oil, mustard oil, groundnut oil, sesame oil and ghee each dominate the regions where their source crop or dairy economy is strongest.
These fats are not interchangeable in flavour: mustard oil is pungent and needs heating to mellow, coconut oil is sweet, and ghee carries a browned dairy note.
Because the fat is present in almost every dish, it colours an entire regional cuisine more thoroughly than any single spice does.
Souring agents are strictly regional
Tamarind, kokum, lime, unripe mango, tomato and fermented batters all supply acidity, and each was adopted where the source was locally abundant.
They differ in more than sharpness, since some contribute sweetness, some astringency and some a fruity depth, so swapping one for another changes the dish rather than adjusting it.
This is why the same vegetable prepared in two regions with the same spices still tastes fundamentally unrelated.
Climate decided what had to be preserved
Hot dry regions developed extensive drying and pickling because fresh vegetables were unavailable for long stretches of the year.
Humid coastal regions could not rely on drying and turned instead to fermentation, coconut and fresh produce available year round.
Those constraints have outlived their cause, and dried and fermented preparations remain central in cuisines that could now buy fresh produce all year.
Community practice adds another layer
Different communities observe different exclusions, with some avoiding onion and garlic entirely and others restricting particular vegetables or foods on particular days.
Cooking developed under those exclusions had to generate savoury depth by other means, which produced techniques leaning on asafoetida, ginger, souring agents and long browning.
The result is that regional variation and community variation compound, so a single state can contain several vegetarian cuisines that overlap only partially.