It indicates uncertainty, and the need to phrase things softly so people don't get annoyed and hurt you. People with more privilege tend to do it less often, because they're less likely to feel a need to defend themselves pre-emptively. It's a habit I learnt in school - teachers will get offended if a child points out their mistakes, but will accept it if a child asks a question that makes their mistake obvious, and it still achieves the result of the mistake getting corrected.