Why do people scream and discuss?

I just hate people discussing in a loud voice. People who when discussing private matters or chatting with fiancee/spouse talks in lowest tone, other than work talk in normal voice.

Was pondering y do they discuss like that
- to show off that they know that particular topic discussion well
- to display that they are busy in more discussions
- to intimate the peers and the boss that they are 'intelligent' and people approach them for opinions- to prove their point
- to keep dominating always
- to boost the sales of amritanjan , tiger balm or axe oil
- to increase coffee/tea drinking people

Even more irritating is when the person with booming voice says
- Keep low voice when we slightly raise a voice in another group!!
- Asking innocently do i raise my voice to reportees - out of concern and if chamcha - to get a NO
In such situations, any onlooker has two options
- Get your eardrum damaged by listening to the discussion, which falls on u by force!
- Get your eardrum damaged by listening to songs over headphone.

I prefer later - Ilayaraja's songs - any day a better, uncomparable bet!!!