Originally Posted by SectionChief

I wouldn't go so far as to say they don't care where you've been.

I'm sure they're interested more in travel patterns to high risk, high threat, high crime countries. So leaving off UK wont bother anyone, but if it seems that you keep going to North Korea and Afghanistan every other week and are less than forthcoming about it, expect a phone call [or a home visit from the suits] about your application.

For super frequent global travelers, it not always easy to remember where you've been, or to be able to read all the stamps in your passport, or to fit all the countries you've visited on the 2-4 lines provided on most visa/entry/immigration forms.