Why Do My Parents Still Talk to Me Like I Am Sixteen?
The brain files a person at the age it first learned them and quietly refuses to update the file. Your parents still use the old tone because of: 1) the primacy effect, the first version of you is the one that stuck and everything since has been filed as an exception 2) role scripts, the family has one script and everyone gets handed their old part at the door 3) loss aversion on their side, promoting you to an adult means admitting the part of their job that is finished. They are not disrespecting you. They are protecting a version of themselves.
What is actually happening
They learned you at sixteen
The house restores the old script
Arguing inside it proves them right
Change the room, not the case
Myth vs Reality
Myth
If you explain how much you have changed they will finally see it
Reality
They watched you change. The old script is just easier than the update.
Notice how fast the old version returns the second you walk through their door.