If ksysguard was invoked from freememorynotifier directly, every process is displayed with its own kill button.
In most "OOM-risky" cases it is required to kill one and only one process.
Clicking on his own "Kill" button is cheaper than selecting it from list and clicking the main "Kill" button (2 clicks > 1 click)
Also, you cannot hide this column by accident or show it when invoked by hotkey (Ctrl+Esc by default).
Since it's invoked with --ignore-config option I implemented earlier (D17217) any layout changes won't be stored in config.