Every time this topic comes up, I'm always confused how the algorithms are biased. Which algorithms? Isn't it actually the labeled data they used to train that

Every time this topic comes up, I'm always confused how the algorithms are biased. Which algorithms? Isn't it actually the labeled data they used to train that is biased by not including enough samples of non-white faces? What mechanisms are in place that prevent literally everyone from just re-training on better data? Why does my toy facial recognition software written in javascript detect every face I throw at it? Many of these pieces smell phony. I'm certainly not saying there isn't institutional racism at work here, but I think we need way more detail to evaluate these claims.