We say ‘hello’ because of Thomas Edison. When Alexander Graham Bell patented the telephone in 1876, ‘hello’ was mostly used to grab attention (‘Hey, you!’). Bell favored ‘ahoy’ as a greeting, but Edison envisioned phones as business tools with always-open lines that didn’t “need a call bell as Hello! can be heard 10 to 20 feet away.” Edison won the battle, but Bell was so tied to ‘ahoy’ that he used it for the rest of his life. Source Source 2 Source 3