International poverty line set by the UN is USD 1.90 per person per day, or SGD 2.60. If PAP Govt are to follow the UN's guideline, they will never come up with a policy that actually help anyone in SG. SGD 2.60 per day means a family of 5 have an annual income of less than S$5000. It's impossibly hard to be below this benchmark in SG.
So when MP Jamus Lim asked why PAP didn't set a poverty line, that's because it will either be at the IPL or way higher. And in SG, while it's pretty easy to earn more than the IPL, it is not easy to have sufficient income for day-to-day living. So, following the IPL will benefit almost no one but setting a line too high and many will be disenfranchised.
Not setting a poverty line is a strategy to make sure the policies made benefit as many people as possible without setting an unreasonable cut-off. Are the policies made perfect? No. But do they work? You tell me.