Ah yes, how dare people walk around after 10pm.
Is it inconvenient to walk around the park? Sure it is. Should people plan for that, knowing about it? Probably. Do people do so? Usually not. Same thing with jaywalking. It isn't the same as "how dare people walk across a street".
They're free to walk across the street - just do so at the cross walk. Likewise, they're free to walk around after 10pm - just not in the park.
The tickets from people ignoring signs is also additional revenue to the town/state so there is some financial motivation to not spend money on a gate (and staff responsible for locking/opening the gate).