> In my setup my laptop is close enough that I can reach out and use the fingerprint reader on it.

Some mechanical keyboards ship with an embedded USB hub that supports a couple of USB ports that allow users to pick and choose what devices to plug in.

I wonder why this feature isn't widespread.

Not arguing with the general usefulness of the USB hub, but Apple chooses to make their Touch ID sensor 100% proprietary, so the inclusion of a hub is a separate topic to the comment you're quoting. There's no USB Touch ID reader, other than a whole dang Apple-branded keyboard (which is wireless but will work as a USB device).