I do agree that everyone has their own commitments out of IF, but I believe that a quick note to the organizers would help a lot. Be aware that some routes are limited; you have the slot so others can’t take it, but you back out 5 mins before the event started. Is this fair for others? And I am very sure that by planning ahead of schedule (a week, three days or even a day prior), ask your parents/yourself: Are there other commitments that I have to do tomorrow? If not, I will be flying during this period of time. If you have something else to do, cancel it so others can have a chance to have your slot. It is only that 30 minutes of your time, there are no requirements for you to be active during the flight (to those who fly short hauls, bear in mind you can get a long haul as well; 20-30 mins is all you need).
In conclusion, be aware of your schedule; if you are (or might be) busy that day, don’t sign up/sign up last minute. If you did sign up, please do your very best to join the event. It is not the best option to just quit last minute, neither being absent during event. A quick look into your schedule helps the entire IF.
Good day and safe flights,