Typically, the modern arcade machines pretty much all used Piano hinges, as well as panel clamps.
Only certain elder models, or small control panels didnt have hinges.
This makes it easier to work on and or replace parts.
I highly suggest the Happ style spring lock clamps. They latch a lot stronger and tighter than the ones pictured above.

And actually, its a bit dangerous not to lock the CP.. If a little kid grabs the sticks and tries to hang or yanks on them hard... they could get injured.
Also, some people rock the sticks quite hard... especially on a game like Robotron.. which can cause the CP to lift and slam down... which isnt pleasant, as well as can mess up on what you are doing.
Finally, I know from running an arcade for 3yrs, that CPs can and do flip up... especially when you forget to lock them down.. >.<