A while ago I met a woman on a plane who was a speech therapist and I was very surprised to find that a lot of her clients were actors who wanted to learn to enunciate words properly.
The majority of the issues she helped people deal with were based on regional / international dialect but, she found there were lots of people who really just didn't enunciate their words at all and that they were aware that their speech made them sound uneducated and less smart. She also shared that she worked with regular people in business related fields who wanted to get ahead and felt the way they spoke hindered them.
I wondered at the person who KNEW they didn't enunciate properly but still had to talk to people regularly. What did that feel like and how did they determine they weren't "doing it right?"
I remembered the episode of "King of Queens" when a woman in the office told Carrie that she might not get a job she applied for because of her "Queens accent" so Carrie tried to work on her diction: