Think about what you would tell a highly capable new colleague on their first day. You would not ask them to start drafting client communications without knowing who your agency is, who your clients are, what your tone of voice is, and what good output looks like for your specific practice.
Your personal context document is exactly that briefing. Written down. Ready to use.
Without it, AI is writing for a generic travel advisor. With it, AI is writing for you specifically: your agency, your clients, your voice, your standards.
The difference in output quality is not subtle. It is the difference between content you have to significantly rewrite and content you are happy to refine and send.