[librarianscott]

It's about etiquette, not about your time. Remember what Emily Post says about hello[1], "On very informal occasions, it is the present fashion to greet an intimate friend with “Hello!” This seemingly vulgar salutation is made acceptable by the tone in which it is said. To shout “Hullow!” is vulgar, but “Hello, Mary” or “How ’do John,” each spoken in an ordinary tone of voice, sound much the same. But remember that the “Hello” is spoken, not called out, and never used except between intimate friends who call each other by the first name."

Saying "hello" is not some devious plan to interrupt you, but rather a thing that humans do rather than act like a bot.

[1]: https://www.bartleby.com/95/3.html