When a new person joins the waiting list, they can refer 10-15 people to Mondo to get to position 1 in the list, and then get their card, thus queue-jumping.
When a person has the Mondo app and is using it however, there are no incentives for them to refer people to Mondo. Take Uber for example. They give £10 in credit to both you and the person you are referring to Mondo.
I feel like if there was an incentive for existing users, people would be more inclined to refer people to Mondo, thus growing the Mondo waiting list even further and customer base etc.