For those who choose to do PII studies, why do you do them and where, if anywhere, do you draw the line?

Everything I've seen in this sub regarding PII studies consisting of posts and comments avoiding them like the plague. Obviously I understand the vague privacy concerns associated with them, but I'm curious about the experiences of those who do choose to engage with them (though I'm basically expecting that to consist of "I just want more money, isn't that obvious?").

For instance, I'm staring at one with a strong pay rate that only collects name and email, which is tamer than some of the other ones I've seen. Makes it more tempting, but I still haven't pulled the trigger on it.