Here's the technical explanation.
The reason calicos are female is because of the orange gene. Also the no-orange gene.
The orange gene is sex specific, ti's passed along on the X chromosone. Males being XY only get one of them. If they get the no-orange gene, they are black and/or brown. Black and brown turn orange in the presence of the orange gene so if they have the orange gene, they will be orange. (there's a reason why more orange cats are male but that's not relevant here)
Females being XX, will get two of the genes. If they get 2 orange genes, they'll be orange. If they get 2 no-orange genes they'll be black and/or brown.
Now here's the interesting part. The 2 genes are not dominant over each other so if a female gets one of each, she'll have both orange and black on her. Black and orange cats being torties and black, orange and white being calicos.
The rare male calicos are genetic mutants, having picked up an extra X chromosone so they're XXY.