I have never had a cold sore, and some people i know get them all the time. I dont just think that its about catching the virus from someone else, i know people who get cold sores from being in the sun too long!
Right basically you can have the virus lay dormant in your nerve endings for years and not show up until your immune system gets a bit low then bam you get a cold sore. You can also catch a virus from someone else and your immune system gets low that way and it comes out that way too.
The chicken pox virus and this are the same thing. Once you have chicken pox then the virus goes into the nerves and lays dormant. Then later in life it can come out either in cold sores or shingles.