And why does a CF-18 have a tailhook?
All F-18s are carrier capable. But on a side note, I believe USAF aircraft have arresting hooks also. There are times when in an a/c emergency, a base may have to use an arresting cable to stop an aircraft in trouble. When I was at Clark AFB in the phillipines, I watched an F-15 have to use an arresting cable on landing.
F-15s and F-16s have tailhooks as well. Mainly used for emergency purposes such as brake failures.