If the only damage is personal (they lose their own money), why can't we make them responsible for their choices?

Because enough people losing their own money in the same way becomes a social ill.

Much in the same way we try to limit physical addiction, which hypothetically only affects the person taking the substance, and gambling (though we're moving backwards on sports betting).

Some hypothetical social ills: 1 If it's a good source of money, it becomes more ubiquitous. This leads to entire illegal markets, which will typically lead to additional crimes, up to and including human trafficking, slavery, organ harvesting, and murder https://en.wikipedia.org/wiki/Scam_center.

2. The victims of scams will often feed shared or even stolen assets into the scam, desperately relying on an eventual return that will never come. This mirrors one of the better known social ills of gambling and addiction.

3. Even for people that never fall victim, defending against scams is tiring, irritating, and damages social fabric. An easy example is how spam cuts down on the utility of phone calls. In general, to be safe you have to be almost irrationally suspicious of anyone being surprisingly friendly, which makes non in-person connections -one of the greatest benefits of the internet - much harder and more dangerous to forge.

What do you think, is that enough reasons?