Why does all life on our planet have these left-handed amino acids?

Actually, it seems that primordial chemistry in the vacuum of space played a major role in what life could evolve on our world.

This is the conclusion of NASA astrobiologists Daniel Garvin and Jason Dworkin who examined meteorites rich in carbon to find the amino acid isovaline. Since isovaline isn’t actively used by living things on Earth and maintains the same chirality over billions of years, scientists can use it to take a look back at the dawn of the solar system and determine the ratio of left-handed to right-handed molecules without the threat of biological contamination. As it turns out, when a meteorite is rich with water, it has up to 18% more left-handed isovaline so when meteors with disproportionate amounts of left-handed amino acids fell to Earth and deposited their organic cargo, they would’ve created a bias towards organisms with our current chirality.