Inhibits prevent DPMS

If the screensaver is active while an inhbit is set (e.g. by manually locking), the monitors will either stay active (but blank), or become active again shortly after locking. This can be problematic especially in cases of stuck inhibits and when keeping your machine powered on over night.

An inhibit will never be able to punch through a lock, so there is little point in allowing it to disrupt DPMS.