Worth Reading: Why Do We Have Native VLANs?
Daniel Dib went on another deep dive: Why Do We Have Native VLANs? What I loved most was that he went through the whole 802.1 standard (quite an undertaking) and explained the reasoning that VLAN-aware switches behave the way they do.
You should also read the follow-up post: what happens if a VLAN-unaware switch receives an 802.1Q-tagged frame?