Talking loudly is often a deeply ingrained habit rather than an intentional choice. Common reasons for elevated volume include:
Difficulty gauging one's own volume due to hearing loss or auditory processing issues. Talking Loud
Growing up in a loud household where one had to speak up to be heard. Talking loudly is often a deeply ingrained habit
While loudness can project confidence or "vocal image", it can also lead to friction in shared spaces: Talking Loud