Yep, I married young, for many of the same reasons. We have been very lucky that we have grown more and more together over the years. It is so easy to get 'unlucky' in this since people change so much from the time they're 18 or so. So many JW kids never realize what 'reality' is until they're living it - with a wife (and many times children) to support.
I have to agree that the motivations are usually hormones, being forced into it (dating is a NO NO unless you are contemplating marriage - so often parents/etc push you towards it). Also the thoughts of marraige being an 'excuse' not to pioneer/bethel/etc might be more prevelant than we think. Most JW kids just want what they percieve to be 'a normal life'. Marriage is the easiest way.
One hall we went to had like 8 or 9 marraiges over one summer - ALL of the teenagers/low-20s got married in a marriage free for all Almost like when one did it the rest paniked thinking all the 'good' members of the opposite sex would be 'taken' soon.