If they weren't getting any pension (aka not having worked their entire life), they'd get welfare, which is about 1000€/month. They'd only have to work if they wanted e.g. a larger flat, or more luxuries. I assume the same is true in the Netherlands: if you get AOW and you want two cars, they don't double your pension but you're free to work and earn money to afford those cars.
The trouble of course is in expanding those programs unconditionally to everyone. If you can get by well enough with 1200€ in the Netherlands, why would a 20yo not opt to live off of the expanded AOW instead of working?