...There should be a mandatory period of flying hours where you can only fly with a more experienced pilot or solo and then have an instructor check-ride before being allowed to carry passengers.
Totally agree.
The Robinson POH has a safety notice SN44 stating that a newly rated pilot should not carry pax until 100hrs and 20hrs solo. Also only to fly VFR in daylight and keep the first several flights local.
Many smart pilots follow this SN44, some don't and within 1-5 hrs after passing they start flying with pax to places they've never been. (not saying the affected pilot didn't. I'm not aware of his experience).