The mostly young wedding guests were killed in a bus rollover at a roundabout in Greta in the NSW Hunter Valley in 2023, with another 25 injured.
Driver Brett Andrew Button, 60, received a decades-long prison sentence for his role in the crash, as he was under the influence of opioid painkiller Tramadol and driving too fast at the time.
Another contributor to the extent of the tragedy was how few of the passengers were wearing the mandatory seatbelts, the Office of Transport Safety Investigations said in a report published on Friday.
Chief investigator Jim Modrouvanos said not wearing seatbelts on coaches was a systemic cultural problem across the community.
"If you are travelling on a coach and there is a seatbelt fitted, please wear it - it could save your life," Mr Modrouvanos told reporters on Friday.
"We must act on the lessons from this investigation to improve road safety and minimise the chances of a similar event happening again."
The chief investigator said his team had found only one fine handed out for not wearing a seatbelt on a coach in the past five years in NSW, indicating even police may require a culture change.
The report found a series of red flags were missed that would have prevented Button getting behind the wheel on the night of the crash.
''The fact he was using (Tramadol) was known to the doctor ... so there were opportunities to report it," Mr Modrouvanos said.
"There were a series of substantiated passenger complaints about the driver's general behaviour ... that could have been acted upon as well."
Mr Modrouvanos delivered 41 recommendations and said he hoped survivors and families of the victims appreciated the efforts investigators made to produce the findings.
"We have looked at every conceivable area, and the loss of their loved ones is not for no gain," he said.
Government regulators, operators and organisations have already accepted wholly or in principle all relevant recommendations.
They include strengthening medication management and developing a database to capture more information about drivers when they change employers, as Button did multiple times.
The NSW government was committed to acting on the report, Transport Minister John Graham said.
''We can't undo the immense loss and trauma caused by this crash, but we learn and change from it - and we are doing that,'' he said.
Transport for NSW secretary Josh Murray said his body had already started delivering on the recommendations.
In November, Button unsuccessfully attempted to reduce his 32-year sentence for the crash.
A court previously heard he accelerated into a turn while carrying guests from a wine estate wedding.
His bus entered the elliptical roundabout on the way to Singleton before tipping over and hitting a guardrail.
"This next part's going to be fun," Button told passengers before accelerating into the roundabout and speeding around the turn before the crash.
Survivors described feeling they were about to die as the bus fell sideways towards a roadside barrier.
"The sensation of falling sideways and being completely powerless was terrifying," one told Button's sentencing hearing.
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