You must come to dinner!

Nothing Fancy -
just pumpkin soup is fine.

In a rare show of wit, Ronald Reagan said that the nine scariest words in the English language were “I’m from the government and I’m here to help.”


For Gore Vidal, the three scariest words were “Joyce Carol Oates”.  (Not a fan of her novels, I guess.)  For  Seinfeld's friend George, "We have to talk".
​
My heart sinks when someone says, “You must come to dinner”.
What is being said here?  Am I naughty that I have neglected to come to dinner? Surely I can only come if I’m invited.
Am I expected to turn up, a bottle of Shiraz under my arm, next Wednesday?  Do I knock on the door and say I’ve come to remedy my lack of manners. I'm here for dinner.  Hope I'm not late.
Why do people say this?
Might it be better to say “I’ll ring you during the week to make a time for you to come over.  Haven’t had a good chat in ages.”
 
“You must come to dinner.”  Stop saying this.
Is it my fault or yours?

---