You're reasoning is way off. There's no "of course" when it's about "visiting" family. 90 days Non-immigrant O Visas for any reason are not actually holidays, because you're not a tourist. Do you even know about the new financial requirements for a 90 days Non-immigrant O Visa based on for example retirement? I guess you don't.
Visiting family isn't the same as staying with family. That's not the definition of "visiting" in my book. And why do they ask about return ticket if "many people do it"? I just want it to make sense. That's all.
I don't believe that's true. No one is "visiting family" forever. Not in my book anyway. To be honest, I don't know anyone applying for a 90 days Non-immigrant O based on "visiting family" and then stayed. It doesn't make sense.