I blame the Nextel phone circa 2001 or so, and then when it extended to boost mobile and a wider audience for conditioning people to get used to this type of thing.
For the younger crowd it was a cell phone with a “walkie talkie” feature. Initially marketed towards contractors and such as a phone that was easier to use on job sites because the walkie talkie feature allowed instant communication rather than waiting for a cell phone call that had ringing and waiting for an answer.
Unlike normal walkie talkies it was backed by cellular networks so the range was basically infinite, the feature worked as long as you had compatible hardware so even if you weren’t on the same plan you could “beep” people, and it gained popularity quickly because this was the McMansion era where contractors were hired en masse by development companies that built the suburbia hell we have now, who in turn were encouraged to buy these phones and also tended to buy them for their families so they could “beep” them too. It gained even further popularity because the “beep” feature often didn’t count as phone usage in an era where unlimited plans did not exist and metered phone and texting plans were the norm. Lots of elder millennials can tell you about the time they got a $1200+ cell phone bill in 2006 talking/texting with their friends or crush, dark times.
I am so glad they died out. It was a scourge. I was in high school at the time and worked in restaurants throughout. In a short time it went from the etiquette being people being mad about cell phone ringers going off constantly to this nightmare scenario of “chirp chirp HEY WHAT ARE YOU DOING” because again these acted as walkie talkies so there was no ringing, it was just a loud ass speakerphone with a person talking, immediately. When boost mobile came around they capitalized on this and marketed it as the “where you at” phone. Terrible