Why is it unlikely that identical twins would have identical fingerprints

because they form a single zygote.

Although identical twins have the same genetically makeup, coming from the same egg and sperm, the embryo devices into 2 in early development. Therefore the small differences in the womb environment give each twin slightly different fingerprint pattern. Also fingerprints are not entirely genetic characteristics proven by have 2 different prints for your right and left thumbs for instance.