Aren't hiragana and katakana named that because they're both modifications of kanji—katakana by taking parts, and hiragana by smoothing out—with ka (か/カ from 加), se (せ/セ from 世), ni (に/ニ from 仁), he (へ/ヘ from ヘ), and ya (や/ヤ from 也) demonstrating the similarity?

And does the history matter to kids who just have to accept that G and g or ぢ and ヂ, however differently shaped, both make a "jee" sound, and end up switching so naturally that they don't even think about it, even as they think the other pair is weird?