Yes, there have always been unwed mothers in any society.
The fact that there is virtually no legal divorce in the Philippines also helps to explain the large number of unwed mothers. A lot of Filipinos don’t want to commit to marriage because they can never divorce. So, they shack up so they can walk away from their responsibilities at any time with little or no legal consequences. I call it "Filipino Divorce".
The fact that many guys have two or more "families", with multiple partners and children, and with no legal marriage contract, seems to be accepted as a way of life in the Philippines. I personally know some Filipinos who know that their parents were never married and dad also has another "family" on the side. They mostly just shrug it off as not such a big deal.
The female partners will often accept this arrangement because it is extremely difficult for a single mother o support herself and her child/children. Many times a female will lose her job simply because she marries or she reaches a certain age, say 25 for example.
The stigma of having a child out of wedlock is real, especially in the rural province areas, but less so in the large cities.
Also, beware of single mothers listed on the dating sites. Some of those women are legally married and you may be deeply involved before you find out the truth about their situation.
Blaming all of this stuff on the Catholic Church seems to be popular with uninformed folks who have some kind of axe to grind.
Ray