It doesn't - it's just considered more polite. Similar to how the plural form "you" became established over the original "thou/thee/thyself" or to the way that

It doesn't - it's just considered more polite. Similar to how the plural form "you" became established over the original "thou/thee/thyself" or to the way that people use the polite/'royal' "We" instead of "I" in a formal paper to point out something that the author did, or argued for, etc. Indeed, there's probably some common mechanism underlying these polite forms in English, as their similarity clearly suggests. (Perhaps an effort at purposeful simplification in the grammar, as the English language has turned into more of a widely-used standard, in Britain at first and then internationally?)