Copywriters use "more than" so they can refer to nice round numbers and make them sound subconsciously larger. "More than 70,000 attendees" means 70,206 attendees, but it could be 100,000! You never see this at smaller scales: "This pack of eggs contains more than 11 eggs!"
"My 2018 birthday party had a year-on-year growth of 17%, with over 6 attendees. More than 80% of attendees said they would attend again next year"
