You know, if you think about it, the Beatles really respected the institution of marriage. All were married starting with John, then Paul, and ?
I think they knew the difference between having a million girlfriends and having one woman (wife) who loves you and is (possibly) loyal to you. I don't know but I feel fairly confident that all the Beatle wives were loyal to their Beatle husbands.
I've always respected The Beatles for this. Even in the early days, I thought: "Wow, with all those women they could choose from, they still ended up marrying someone!"