What Happened to Illegitimate Births?

From 1660, there was a major increase in illegitimate births until about more than 25% of first births were illegitimate by 1800. Historians have been debating this for decades, what changed? One reason could be that people intended to get married had sex as a normal part of we're getting married. But then something happened to stop them getting married. Or they might have said, Oh, you move, get a job, I'll come and find you later. And so then you have another legitimate child. Another thing, which historians are still undecided about, is some kind of sexual revolution. So like the 1960s, over the 18th century, there was this much more accepting culture of