Two reasons from my perspective, other than my ears are getting older: 1. The sound mix has a huge dynamic range now, and lots of action scenes are mixed in with quiet conversation. Set the volume down, and you miss the dialogue. Set the volume up, and you wake up the neighbors. 2. Dialects and accents seem to be more prevalent in content, and CC helps to cut down the cognitive load of “translation” while being enter…
I was once told, by a salesperson in a TV store that this was essentially "by design" and that the solution they're taught to present is to "buy a soundbar". From his understanding, in the quest to get thinner TV manufacturers sacrificed built-in speaker size and quality, which results in the effect you describe. I am not sure how much is sales patter and how much is truth...but I bought a sound bar!