It's because most Filipino applicants apply for the wrong type of visa, and they don't know the exact definition of the visa category they're applying for, which results in a high percentage of visa refusals.

Few examples of applicants who applied for a B1/B2 tourist visa:

1. A skilled worker who considers the USA as a greener pasture, and tries to apply for a tourist (B2) visa, for the purpose of getting under-the-table work there.
2. A Filipina wants to meet her American boyfriend whom she has known online and not even met in person. The immigrant visa takes too long so they go for a B2. This is so common in the Philippines, and US consular officers are very familiar with this game.
3. A person who has family members in the US who are out of status (overstayed their visas), so it is (also) unlikely that he will be issued a visa. Guilt by association.
4. A professor who has a high educational background, but he couldn't explain clearly in the interview the purpose of his travel to the US.
5. A young man who submitted fake documents in support of his application, not knowing that the consular officers are trained well in detecting fraud.
6. The Filipina who is already married to a Filipino but submits a fake annulment paper in her K-1 application with a man twice her age thinking the US Embassy won't check. (That's the first thing they check)
7. A wealthy businessman who has paid for the assistance of a cheap immigration consultant - he was told to give long memorized answers- but still refused a visa.
8. An old lady, who literally pleaded for a visa during the interview with the visa officer - with the intention of visiting her grandchildren in the US. She has made herself so desperate to go to the US, so she was refused.
9. A middle-aged man who says he has a successful business yet is using carabao English during his interview.

Notes:

The Philippines is #1 in the world for B2 visa holders applying for adjustment of status (trying to stay)

There are more TNTs in the US than any other group except for Mexicans

There is a large thriving Filipino middle class - Its just that it lives in California.

Getting a US visa should be taken similarly to passing a board licensure exam. You do not increase the chances of getting it when you apply several times. In fact, the mountain gets taller with each denial as it indicates that you're desperate for a visa. If you're really qualified, you can get it in one shot.

Do not lie in your application. Tell the truth. Walang sikreto sa pagkuha ng US Visa.