I am now going to get on a soapbox and make many enemies.
Later these people may or may not thank me.
No one who has never turned a lap on the track has any business at all on a modern litre bike at a track day. No one.
There have been three track day deaths this year. I know that at least one of them was riding a litre bike. Every track day organizer I've worked with has safety at the forefront of their program. However, as Chris said, this does not weed out the Darwin Award candidates. It doesn't in racing either, but there's an "understood" tighter structure. Not to mention that experts can and will bitch to the right people until the "issue" is dealt with.
I understand that as a business, track day organizers cannot turn away guys on litre bikes, it would be financial suicide. So here's my not-so-perfect idea.
If you show up with a litre bike and you are not known as an experienced rider by the coaches and staff, you ride Beginner. Exception: Expert licence with CCS ASRA WERA, etc. If you have an AM/Novice licence, you ride beginner. (this is the "maiking enemies" part) Why penalize everyone? Because people DIE. Period. So a vetting proccess is necessary. After an evaluation session, these riders can get placed properly. K3s newbie would never make it out of begginer until he gets an attitude adjustment. Guys who can ride should have no problem moving up to the next levels offerd by the track day for the rest of the day(s).
Yes, guys can get killed on smaller displacement machines, but the attitude of some riders about litre bikes is the issue, and you need to weed out the guys with a chip on their shoulder.
For example, the modern 600 behaves more like a 750 or 1000 of 10 or so years ago, with better technology in the frame suspension and tires. Litre bikes are like souped superbikes of a decade ago, again with all of the advances thrown in. These are the kind of machines that only world class racers could get their hands on "way back". Now you have green novices who hold an probationary operators permit that's still wet able to purchase one of these monsters. Then they decide they want to "learn" during a trackday, but close their minds to the possibility of actually absorbing some of what good experienced riders want to teach them.
The other class of Litre madness is the mid-life crisis guys. These guys tend to buy the most high powered bike they can afford, most likey the Hyabusa.
We all know how appropriate that 1300cc monster is for the street or the track. Mind you, these are the guys who rode Honda CL350s in highschool and college. No clue.
So yeah, I think the process of weeding out potential problems this way allows trackday orgs to control a potential problem while still allowing the patron a little bit of glory. And hopefully, it also gives them an additional opportunity to educate those that wish to learn. Let's face it, bikes are just about one of the biggest pleasures we know of, let's spread the love while keeping 'em safe and in one piece.