Since I am certain it will be deleted, I will set it out below:
Because the laws in the West encourage it in the name of feminism, which no man is allowed to question, or he will end up losing his home, half his property and access to his children while having to pay for them until they are 18.
The West is also The Land of Bastards, Bastardy, Welfare Claimants and High Crime, ruled by the ideology of Feminazism whose Sacred Cow is Single Motherhood (which includes Divorced Mothers as well as Never Married Mothers).
Successive governments dare not address the harm caused by single parenthood because that would be tantamount to blaspheming against Sexual Freedom Without Responsibility, a deity every Westerner is expected to worship unquestioningly.
Primary schoolchildren are prepared for Sex Worship (in the form of Sex Education). As soon as they are in secondary school, they will be shown how to do it, and handed contraceptives at regular intervals, to encourage them to do it.
In the UK, girls under 16 can get contraceptives through their doctors and pharmacies, who are not obliged to inform their parents.
Single mothers, as we all know, are the ones who are most busily breeding the next generation of under-achievers, prostitutes, criminals and welfare claimants.
[As proof of this proposition that you cannot blaspheme against Single Mothers and Feminism, you will see this answer briefly, then it will be deleted by the Yahoo Guardians of Political Correctness, on grounds of causing offence to Single Mothers and the Illegitimate, who now make up about half the population.]