I guess the main reason is they don't earn much income from their job, most the filipinos who really aim to have higher income are just going abroad as they earn better and they have better opportunity, and other thing is lack of discipline to save, since the first step before you'll be able to invest, is you need to start saving first, if they failed in the first step, it's not possible they'll be able to invest, unless they'll take a loan to invest the money, which I believe not advisable.
I know someone who is earning a relatively small income but he still managed to save and invest his money (which eventually led him to become successful in his career). The problem stems from the lack of knowledge when it comes to investing. There are little to few business/investing seminars in the country and most people invest impulsively without researching.
If the person is determined enough to invest, gagawa at gagawa ng paraan yan kahit magkano man ang kanyang income.
Basing from my experience, I invested bitcoin sa USI-tech and it became a ponzi scam pala. Natuto na ako and mas naging careful ako whenever mag-iinvest ako ng pera. In fact, mas na-inspired pa akong mag invest after kong matalo dahil at least, alam ko na mga iiwasan at gagawin ko.