Very limited write access through EmbSys Registers

I am using the EmbSys Registers Eclipse plug-in to view the nRF51822 register values. The majority of the registers allow read only. Why isn't the access set up so that more of the registers can be written to through EmbSys Registers UI? For example, I can't set a pin through GPIO->OUTSET because access is RO. Why isn't access RW?