They were not removed deliberately. Greek sculptures are thousands of years old and have undergone considerable natural wear over time.
Author: Spencer Alexander McDaniel
The statues we see in museums today are almost always beaten, battered, and damaged by time, exposure to the elements and Vandalism. Parts of sculptures that stick out, such as noses, arms, legs, and other appendages are almost always the first parts to break off. Other parts that are more securely attached, such as heads and torsos, are generally more likely to remain connected to the original statue.
Greek sculptures as we see them today are merely worn-out husks of their former glory. They were originally brightly painted, but most of the original pigments long ago faded or flaked off, leaving the bare, white marble exposed. Some exceptionally well-preserved sculptures do still retain traces of their original coloration, though, and, even for the ones that do not retain visible color to the naked eye, archaeologists can detect traces of pigment under an ultraviolet light using special techniques. There are also dozens of references to painted sculptures in ancient Greek literature as well, such as in Euripides's Helen, in which Helen laments (in translation, of course):
"My life and fortunes are a monstrosity,
Partly because of Hera, partly because of my beauty.
If only I could shed my beauty and assume an uglier aspect
The way you would wipe color off a statue."
However, in the nineteenth and early twentieth centuries, classical scholars and art historians tacitly denied that Greek sculptures were originally painted, despite overwhelming evidence to the contrary, because, perhaps influenced by contemporary racialist ideology, they believed that “white is beautiful” and that the whiter something is, the more beautiful it is. This may sound ridiculous to us today, but it led museums such as the British Museum to scrub Greek sculptures, including the Parthenon Marbles, to remove all traces of pigment, which they interpreted as “dirt.” In the late twentieth century, scholars finally began to open up to the fact that classical sculptures were originally painted and this fact is now widely accepted, albeit only begrudgingly by many, who prefer the sculptures in their current lily-white state.
Many Greek sculptures were also originally holding objects made of precious metals, such as scepters or weapons. These were almost invariably stripped away from the statues long ago, during times of economic hardship when such metals were needed to fuel the economy. Towards the end of the Peloponnesian War (431–404 BC), the Athenians stripped the precious metals from their own Acropolis to fund their war with the Spartans. The Phocians did the same thing to the temple of Apollo at Delphi during the Third Sacred War (356–346 BC). This is the reason why Greek sculptures are often in awkward or unusual poses, because many of them were originally holding things.