Not having a tube allows the tire to flex more so it’s more compliant. It’s not that you’ll avoid punctures, but that they often seal themselves. Tubeless definitely isn’t necessary and probably isn’t super beneficial for most people but there are definite advantages for some uses.

Most users of tubeless tires I know ride mountain bikes and on pretty aggressive trails. As the other comment stated it’s not about avoiding punctures all together but they are significantly easier to repair and ride through.