I know that "Would you mind… ?" (the Present Conditional) is more polite than "Do you mind…?" (the Simple Present), and also, that they have to be completed this way: "Do you mind if I do sth?/Would you mind if I did sth?" (asking permission), and "Do/Would you mind doing sth" (a request).
But why does
"Do you mind if … ?" occur more than "Would you mind if … ?",
"Do you mind doing … ?" less than "Would you mind doing … ?"