Same advantage as a drive-in theater! When you pay by the carload, you don't have to hide half your friends in the trunk/boot (not that I ever did that as a teen).
Many shows have handicapped parking and some, like Oshkosh, have mobility scooter rentals. Much harder to get around on grass for those with limited mobility, and it can be quite a trek to get to the flightline at some shows. Potential attendees may not have sufficient endurance.
It is awesome that your dad was able to attend.
Thomas_Mac wrote:
The London Ontario airshow was a few weeks ago in a similar format and I absolutely loved it! Highlights included the F-35, F-16, F-22, A-10 and C-17 demo teams as well as the Thunderbird's all flying from Selfridge AFB. My dad has some mobility issues and hasn't been to an airshow in years, with the drive-in format he could join us and had a great time. I sent them an email saying I hope they keep this format at least in some capacity in coming years. We paid $150 for the front zone and thought it was great value considering we could bring our own food and drink.