I don't think I'll be able to do satisfactorily answer that question in a couple sentences, but I'll try.

White people are a majority in technology, so it's assumed to be obvious to white children that they too can be a technologist. There's not a significant gap in perceived identity between themselves and Mark Zuckerberg, for example.

So, that begs the question, why focus on encouraging specifically white children? They don't face racial barriers and have many famous role models. Preference for white people has a long and ugly history in America.