For most of clothing history, the youngest person in a household wore no garment in the modern sense. They were wrapped. A square or long rectangle of cloth was folded, tucked and knotted around them, and the same piece of fabric later became a shade, a pad, a blanket, or the band that held the child against an adult's back. There was no pattern, no sizing, and no seam.
This is easy to file away as a matter of simplicity. It is better explained as a set of sound structural decisions, and as a good answer to a specific problem: the wearer changes size every few weeks.
A seam is a weak line
A stitched seam joins two pieces of cloth along a single narrow line. It is where a woven fabric is perforated by a needle, where two layers of different orientation meet, and where a pulling force concentrates. Clothing fails at seams far more often than in the middle of a panel, a pattern described in where a garment wears out first.
A wrap has no such line. The load of holding the child is spread across the full width of the cloth, and the cloth is used in the direction in which it is strongest. Tension is adjusted by how the ends are tucked, pulled or knotted, not by cutting the fabric to a measurement. If the child grows, or another adult wraps the same cloth differently, the fit changes without a single stitch being altered. The same logic sits behind the rectangle that became a robe: use the whole width of the loom, and let the arrangement do the shaping.
The back is a load path
When a child is carried against an adult, the question is not only how the cloth grips the child but where the adult ends up carrying the weight. A broad band over the shoulders and around the torso spreads the load over a large area; a narrow cord concentrates it. Traditional carrying cloths are wide for this reason, and they are usually wrapped so that the child sits high and close to the adult's own centre of mass, which makes the combined balance easier to manage while walking or working.
The weave matters here too. A cloth with a little diagonal give can be tensioned firmly without becoming rigid, so it holds a shape while allowing movement. A completely stiff panel would be easier to fold once and harder to adjust continuously. In many parts of China a square of cloth with long ties at the corners serves exactly this purpose; elsewhere a long woven wrap is wound several times so that each layer shares part of the load. The forms differ, the load path is the same.
One cloth, several jobs
A sewn garment has one shape and therefore one main use. An untailored panel can be reconfigured during a single day: wrapped for warmth in the morning, opened as a shade in the heat, folded as a pad on the ground, knotted as a carrier when the adult needs both hands. When one corner wears through, the cloth can be turned so the worn area sits somewhere less loaded, or patched with the same material. It washes as a flat sheet and dries faster than a lined garment with enclosed seams.
That versatility is also a record of an economy in which cloth was expensive. A woven width represented hours of spinning and weaving; cutting it into shaped pieces would waste the offcuts and fix the investment to one size of one person for a few months. Keeping it whole preserved the option to use it for something else later.
Why tailoring arrived late for babies
Infant clothing sized by age depends on cheap fabric, standard measurements, and a market that can supply many nearly identical small garments. Before those conditions, sewing a fitted outfit for a body that would outgrow it in weeks was a poor use of both cloth and labour. Wrapping was not a primitive stage waiting for tailoring to replace it; it was the better solution to the problem as it actually stood.
Seamed infant clothes eventually became universal, but the older idea never disappeared. A modern woven wrap is still a single long panel with no buckles, sized by the adult rather than the child, adjusted by tension, and useful long after it stops being used for carrying. The design is old because the reasoning is still correct.