Increased soles were by Greeks (cothurni) and Romans used to make appear Gods figures higher on the scene.
A separate heel would come later to prevent riders (knights) would slide trough the stirrup when mounting their horses with their feet.
In steps and walk heels should absorb a lot of pressure. A heel can absorb shocks.

schoenstijgbeugelAround 1660 the men wore at court (red) high heels as a status symbol: you cannot do any work on heels, so it was a sign of luxury and wealth. Louis XIV also used this costume to look bigger. A higher heel was a higher status. The word stumbling block would find its origin there.

Because we find it sexy many ladies buy unhealthy high heels which they can hardly walk. High is 7-8 cm. But 12-13 exist. Or extreme. The toll for a tempting mockery with the buttocks to the back and the breasts forward can lead to shortened calf muscle, cramps, hollow back, cartilage wear and low back pain, risk of falls and sprains.
Very elegant and beautiful, but in moderation. Not suitable for 24/7.