Checking tickets can be done by not allowing anyone on the platform. Or world best practice is random checks and large fines if you are caught without a ticket.
Breaking rules is tricky. There is some need for that, though there are options, though in the end I will grant you this.
Trains should never serve food or drink. Passengers can get off the train at a station when they need that, and get on the next train. Space used for the food and drink is space that could be used for more seats. There is a reason all railroads have been trying to do away with food and drink service. It is considered bad practice everywhere.
> There is some need for that.
I see.
> Trains should never serve food or drink. Passengers can get off the train at a station.
There aren't going to be stations all across Nebraska or what have you. And even if there were, stopping repeatedly would defeat the purpose of high-speed rail. All that time speeding up and slowing down starts to add up very quickly.
It doesn't take long to unload and reload a modern train. France and the US do bad, but there are better examples where it can be done in a minute.
* Check passenger tickets
* Observe the cars & make sure people aren't breaking rules, etc
* Serve food/drink if applicable (e.g. for business class)
And so forth. This is how the KTX and Shinkansen work, and they know what they're doing.