usb - What's the reason Android Reverse Tethering require root?

From what i know:

1. Android Tethering, share internet from Android to laptop via USB cable works without root.



2. Android Reverse Tethering, share internet from laptop Ethernet to Android via USB cable require root.

So I'm curious what's the technical reason/limitation of Non-root Android Tethering is allow but not vice versa.