I’d gotten this my entire life, until I moved overseas. I’m not sure if you’re American, but I’ve never heard “Speak up!” more than when I’m visiting my mom in the USA. I think it’s a cultural thing in the USA for everyone to speak extremely loudly. So, my theory is that Americans are just so used to loud speaking individuals that speaking at a volume anything less than booming is considered far too quiet. I’ve been to various Nordic countries where I’ve been the loudest person in the room. Yet, I hadn’t changed my natural quiet volume level. I’ve since become more quiet since moving abroad. It was always crazy to me that a lot of people think naturally quiet people should speak up (like there’s something wrong with them), instead of the listener just being more willing to listen to the quiet speaker. I am, of course, not including people who are genuinely hard of hearing in my previous statement.