"of" seems to be pronounced with the f sound asˈäf in phrases like "of course". But 'of' is pronounced as \əv in a lot of other cases.
Yet, Merriam Websters gives the one with 'v' sound as the only pronunciation.
Why is that? Why does the dictionary give the one with 'v' sound as the only pronunciation?
In what cases 'of' is pronounced with f versus pronounced with v sound?