Increasing numbers of young people leave home while still single, especially since the growth of universities in the 1960s. They are more likely than in the past to meet partners from different backgrounds.
They are away from parental supervision and are not financially independent so are more likely to cohabit than marry.
Secularisation has led to the weakening of religious beliefs about sexual morality, making marriage seem less necessary to many.
The availability of free contraception on the NHS, especially the pill since the 1960s, has increased sexual liberation.
Educated women are keen to establish careers before contemplating marriage and children, and some do not have these as goals at all.
Instead of following the life course of their parents (job, marriage for life, children), young people contemplate a wide range of possibilities (reflexivity) and create the lifestyle they want (projects of the self).
The rising cost of weddings may be a disincentive to some couples.