Then just give a good reason as to why people go. But don't say anything that can be easily debunked. For example, don't say;
A) To see racing. Because if you want to see the racing watch it on TV. You will miss most of the action sitting at the track.
B) To see the cars up close. Because if you want to have a good look at the cars, again, watch it on TV. If you're at the track you'll be absolutely nowhere near the cars.
C) To know what is happening around the track. Because if you want to know what's actually happening, again, stay at home and watch it on TV. You will get pit reporters, people in the paddock, up to date weather forecast etc. Being at the track is putting yourself in an information vacuum.
Television coverage replaced being at the track for seeing racing years ago. Especially as being at the track has become less of an experience as years go on. Safety fences and seating positions make it hard to know what's going on even when the action is right in front of you. But at least you could still hear the cars.... At least until this year.
So go on, give a good reason as to why people cough up thousands of dollars for less of an experience than what they can already get at home. Because the only thing I can think of is the one thing that the television cannot and could never capture; The sound. It created the atmosphere of being at a race. Take that away, and what are you getting for your over priced ticket? The empty seats at recent races should give you your answer...
To see it in real life. Sure you can see the cars in close detail on your TV screen, but it still isn't quite the same as seeing them with your own eyes.
To get the atmosphere of the crowd (at the right venues of course).
To have a fun day out with your friends/family.
It can be good fun to follow a race live at the track in the "information vacuum". Keeping track of gaps and working out if people have pitted is part of the fun too.
The smell. TV can approximate the sound of even the old cars. It can not recreate the smell of burned rubber, oil, fuel, and all the other smells of the racetrack.
To be able to say "I was there. I saw it" when your favourite driver takes a historic win, or whatever historic moment could happen right in front of you.
In my memories of my first Grand Prix, Jerez 1997, the sound was incredible, but it's not the top memory of the race.