Who decided what to adorn?

Well, that depends

Look at these earrings

that beautify different parts of the ear.
Gold, with applied ornament and pendants.

Take anklets, for example.

No other culture uses them as well as India

Less is more?

Nay, more is more.
The Hindu temple is conceived as a heavenly abode for the presiding deity. The building's stepped, indented, and towering exterior evokes the mountains of Indra's heavens, home to the assembly of gods as well as celestial beauties, dancers, and musicians.

Anklets in Sanskrit: noopuram

Mani nupura dhari (he who wears pearl anklets)

Bejewelled insights

Jewellery as a way to understand a culture
Neck chain, gold set with a ruby in hand shaped pendant.
Pair of Bangles

Regional jewellery

Rooted in the soil and the people

In that sense, jewellery conforms to the notions of alankara and aabharana