Legumes carry a great deal of vegetarian cooking, and the reason is textural rather than nutritional. A pulse can be made to behave in several quite different ways depending on how it is handled.
Three components behave independently
A dried pulse consists of a starchy interior, a protein fraction distributed through it, and an outer skin made largely of fibre that does not soften much.
Cooking affects each of these differently: starch swells and gelatinises, protein sets, and the skin either stays intact or splits and releases what is inside.
Whether a finished dish is creamy, firm or fibrous is decided by which of the three ends up dominating, and that is a matter of method rather than variety alone.
Split and skinned pulses collapse deliberately
Removing the skin and splitting the seed lets water reach the starch immediately, so the interior swells and disintegrates rather than holding its shape.
The result is a thickened, homogeneous body that carries spice and fat well, which is precisely what a dal is meant to be.
Cooking such a pulse expecting whole pieces will never work, since the structure that would hold them together has been deliberately removed before it was sold.
Whole pulses hold shape and provide bite
An intact skin restrains the swelling interior, so a whole bean can be cooked until fully tender and still present as a discrete object with resistance.
That resistance is the closest textural analogue to a piece of meat, which is why whole pulses anchor dishes that need something to chew rather than something to spoon.
Overcooking bursts the skins and turns the dish into an accidental puree, so the window between tender and collapsed is the thing being watched.
Soaking and water chemistry change the outcome
Soaking hydrates the interior before heat arrives, so the seed cooks evenly rather than softening outside while the middle is still hard.
Hard water and acidic ingredients both slow the softening of skins, which is why tomatoes and tamarind are usually added after the pulse is tender rather than before.
Alkaline conditions do the opposite and break skins down quickly, which is useful when a smooth result is wanted and disastrous when it is not.
Frying and drying create a third texture entirely
Pulses that are soaked, ground and then fried set into a firm, porous structure, because the protein coagulates while water leaving as steam creates internal spaces.
Roasting or frying whole pulses drives out moisture and produces brittle crispness, which is a texture no fresh vegetable can supply.
Between creamy, firm, chewy and crisp, a single family of ingredients covers most of the textural range a meal needs, which is why it appears in so many forms on one plate.