I agree with codda - in all honesty, iMovie doesn't take up a ton of space, so it's really not a huge issue.
I'm not sure about the newest version of iMovie, but the version I have is ~120 meg. FCPX is ~1.34 gig (per the app store). FCS3 (the previous version of Final Cut along with all of the other tools) takes ~50gig (if I recall correctly, it's been a long time since I installed it - I remember the size from FCS2 as being ~50gig, and I am pretty sure FCS3 was about the same) for a full install. So iMovie just really isn't all that much in comparison and it's convenient to have just in case.