Well, firstly, because they are not in a similar position to yours with regard to this fact unless they are of a similar attitude and skill for promoting these transmissions to human-side visibility. (If you know that they do have the same attitude as the one you expressed, then the "you know they're okay with it" exception applies.) There are a lot of things people "broadcast" in the physical world which are socially expected to be politely ignored as well.
Put another way, your statement makes perfect sense if you assume all software is actually a User-Agent in the traditional, ideal sense. But this isn't so, because even programmers don't generally have the spare cycles to rewrite everything they come in contact with, and non-programmers have an even more vanishingly small chance to do anything about it. Agency in the digital world is inevitably shaped by other people's decisions as represented in software, and social agency is shaped by how that software presents itself not just to you but to the people you're communicating with through it. When the state of the software doesn't exactly match the state as visible to the participants, the latter state prevails in a social context, and it's the responsibility of a polite conversation partner to not mess around behind the curtain unless you already know you're welcome.
Put another way, your statement makes perfect sense if you assume all software is actually a User-Agent in the traditional, ideal sense. But this isn't so, because even programmers don't generally have the spare cycles to rewrite everything they come in contact with, and non-programmers have an even more vanishingly small chance to do anything about it. Agency in the digital world is inevitably shaped by other people's decisions as represented in software, and social agency is shaped by how that software presents itself not just to you but to the people you're communicating with through it. When the state of the software doesn't exactly match the state as visible to the participants, the latter state prevails in a social context, and it's the responsibility of a polite conversation partner to not mess around behind the curtain unless you already know you're welcome.