Discounting even issues of appropriate vs inappropriate, and issues of intimidation, there is also the simple job factor.
Put simply, being an editor is a job, and writers are the suppliers offering their products to the editor to sell. It is up to the editor to select the best products from the best suppliers if they want their own work to be successful.
Accosting a person and demanding their attention at inappropriate times in a context like this states, quite explicitly, "regardless of the quality of my product, I will be a difficult supplier to work with and will demand a disproportionate amount of your time.". I can hardly blame editors for not wanting to publish writers like that.
And besides, when most people are not at work - when they are at lunch (whether in a buffet in public or not) or when they are on the toilet, they do not want to still be dealing with their job. Acknowledging that people need time away from work concerns is just part of being a basically decent human being.