[nine_k]

Maybe their having the least to spare is a consequence, and poor impulse control is the cause.

Anyway, it's like making money off other human deficiencies, say, poor vision or dyslexia, and mistakes made due to those. It feels unfair, it does not feel like a conscious choice. Hence the understandable backlash.

[Dusseldorf]

That doesn't feel like a very apt analogy. Poor vision or dyslexia can't easily be hijacked into a cycle of addiction the way poor impulse control can. Making a bit of money helping someone with poor vision is very different than blasting advertisements on every single medium and using predatory practices to draw in those with poor impulse control. Not to mention the continued exploitation afterwards until the victim has nothing left.

[nine_k]

Making money helping people with poor vision (selling glasses) is fine, of course. I mean exploiting their weaknesses, like using a tiny typeface to write important price information while showing a big price-like number prominently. Doing something formally correct which turns into a trap because of the customer's disability.