Why was scale armour mainly used by elite warriors in ancient Mesopotamia, Palestine, and Egypt?

In ancient Mesopotamia, Palestine, and Egypt, the use of scale armour was primarily restricted to a small elite because it was an expensive form of military technology.

While scale armour provided effective protection against weapons like arrows, spears, and maces, the process of casting or forging numerous small metal plates and sewing them onto a padded fabric backing was a costly and labor-intensive endeavor. Although these scales were technically easier to produce than items like helmets, the overall expense of materials and the time required for assembly made this specialized body armour inaccessible to the average soldier, reserving it for those of higher status or rank.1