It's not that the old lady can't think.
Son has been giving the mother monthly allowance of $600 cash in the past. Then he became smarter and turned to his mother.
Son: Mom, I can afford to give you either $600/month in cash or cpf life gives you $630/month. I recommend $630/month since you get much more.
Mum: Sure of not? Where you learn that from?
Son: Oh, I heard from BBC in hardwarezone and I think it’s a good idea. In giving you allowance through CPF, you get more and I get tax relief.
Mum: You mean HWZ also got BBC? Whoa so good

I have been skipping the manicure and pedicure downstairs. Now with the extra $30, I can afford to go for that on a regularly basis especially now that I am going on dates.
Son: Sure, you can go for it as long as you live. So you agree to get your monthly allowance through your CPF? Ah, but make sure, I am your sole nominee. Otherwise, what I put into your CPF will be shared with my siblings or go to your date, if you stop going for your manicure and pedicure.
Mum: No worry son. Can I also put extra $600 cash into my CPF so that I will get even more?
Son: Sure. The more you put in, you get more than what you put in and for life.
Mum: Ok, I will trust you son.
Comes next month.
Mum: Hey son, how come no $630 from CPF.
Son: Oh I too kanchiong and forget to explain fully what I meant. …………… Nevermind. Forget what I said. I will continue to give you cash. On second thought, I give up the dumb idea cause I need to deposit a fairly large sum at one go.
Mum: WTF, forget what dumb plan you have. I don’t care to know. Just give me $630 cash from now on. I already booked to start my pedicure and manicure on a special discounted price on the first Saturday of every month for life
For the mother to receive payout of $630 for life, the son need to top up a fairly large sum and let that grow over over years before payout begins. If mother is nearer PEA or already passed PEA, an even bigger sum need to be topped up to get $630 the following month.