Because it's a relatively easy way to earn money.
Just to give you an idea of what life is like in the Philippines.
1.5 years of calculus along with all the other classes.
A more realistic job is a teacher and they earn about $422 a month.
In addition if you screw up there are 10 other people in line that want your job so you have very little bargaining power with the boss.
(Source: ) This is why you see even highly educated professionals that will scam foreigners in order to leave.
If a Filipino engineer scams a foreigner for a green card she/he can support his entire extended family on a single US engineer's salary.
Now we haven't even talked about the uneducated that couldn't afford to go to school and the only asset they have is their bodies.
So imagine yourself you have no higher education your job prospects are low and if are you are one of the lucky ones that does manage to find full time work you're making maybe 0-200 a month doing hard back breaking work!
By the way neither of these scenarios are counting the horrendous stress of living in these major cities.
Manila has one of the longest commute times in the world!
(source: ) Now imagine you are already skinny and petite which is what most foreign men that visit Asia are looking for.
All if you have to do is tell some desperate divorcee 2-3x your age that you love him and can't imagine life without him, hit him with a sad story about your family not having enough to eat, you need to pay your little brother's tuition etc, and then the money starts to flow in.