Usually last names only are used by journalists after the first time. Therefore you see one name it's usually the last name with no title. The exception is VERY

Usually last names only are used by journalists after the first time. Therefore you see one name it's usually the last name with no title. The exception is VERY famous people with unique first names like Oprah, Elon, LeBron. I suspect the reason people say "Bill" and "Tim" is because these companies have 100K+ employees for whom using their first name is the norm and expected (for example would be weird to watch management use anything else with each other at all hands meetings), and they do it in public too, so other people on the tech internet do it too.