Affordability, convenience, security. Choose two.
It's not patronizing, it's how the consumer electronics market works and how consumers vote with their wallet.
Consumer device are sold with USB cables that pass data and power lines for cost and convenience, so they can also transfer data while also charging their device with the same cable that came in the box and not have them go out and buy another cable.
Can you imagine being sold a phone who's cable only passed power lines and not data, "for your own security"? The consumer confusion and outrage would be massive.
If your threat model seama it, the solution is buying a USB condom which only passe through the power lines, not the data ones.
Just like the internet and TCP-IP, USB was designed from the start to be as cheap and convenient as possible, before anything else, to get market traction, which it did. Security concerns came much later.