I think the main difference between built in jacks on laptops and this expansion card is that this needs to have all the circuitry to be a USB ethernet adapter

I think the main difference between built in jacks on laptops and this expansion card is that this needs to have all the circuitry to be a USB ethernet adapter on top of the actual jack. I imagine it's a challenge to fit that in alongside the jack itself, although hopefully people will keep iterating on the design - maybe we'll see a better third party one if the Framework laptop is successful enough.