Unfortunately buying a ticket and booking a hotel is necessary in most cases. At the embassy for your first short-term visa and for border control.

I'm a nobody from a 3rd-world country and have always done that with 100% success rate over a decade. I keep visiting the US regularly and I always have a way to somehow ensure I intend to leave the country. The questions at the border keep getting shorter and quicker every time.

Unfortunately, that's how it works, in my experience.