The current rules (as it was in Robot Wars) are clear that gas must be able to be turned off or on and access panels opened without the use of a tool. The idea, as has been voiced, is speed of operation. Links and dump valves should be very close to the surface so hands don't have to go in the robot to kill it.
For example, although I have to put my hand inside Pressure to operate the gas valve, the link and dump valve are immediately behind the access panel, so in the event of an urgent kill requirement you can yank the link and dump the gas safely.
The gas valve, link and dump valve of Skink are all right behind the access panel.
The gas valve of Pressure mkV will be at the surface.
It makes sense, when a robot is designed, to put everything within immediate access so anyone can kill a robot if need be, using tools is inherantly slower.