I suppose that Ozzie Nelson woke up one day and decided maybe there's more we can squeeze out of the Ozzie&Harriet wholesomeness formula. So Ozzie's Girls was born with Ozzie and Harriet becoming surrogate parents to a pair of female college student boarders. After a quarter of a century these two were to become parents of daughters so to speak with that entails.
As a concession to the times one of the girl college students that was boarding in David and Ricky's old room was a hippie chick Susan Sennett. Another concession was that her roommate was Brenda Sykes who was black. No one was going to criticize Ozzie for not being with it. But the two girls were the last word in wholesomeness as each episode showed.
The formula that Ozzie&Harriet a success on radio and television from the 40s to the early 60s was just too old fashioned. A country that was dealing with Vietnam for about a decade at this point and starting to deal with Watergate just was not interested in buying this particular product.
It was a nice show, but way too old fashioned.