why not partir de ?

Question

In the last sentence I typed "quand ils partent de mon salon !" but "partent de" marked as an error and advised "quittent" or "sortent de".

Could you please explain why "partent de" cannot be used here as an option ?

For "partir", in the relevant lesson, it is written as: "When used with a place, it will always be followed by a preposition (e.g. I leave from / for = Je pars de / pour)" Example: Je pars de cette ville.

Accepted Answer

Bonjour Melih,
You are right that, in theory, it isn't wrong. You can come across similar sentences, such as:
Je suis parti plus tôt du concert = I left the concert earlier
Il est parti de chez moi en claquant la porte = he walked out of my house slamming the door  
The fact is 'ils partent de mon salon' is by far less "elegant" than using 'quitter' or 'sortir de'.   
I hope this is helpful.
Bonne journée !