For every human who thrives on novelty, there are a hundred who quite deliberately engineer lives of stasis and routine, or at least as much stasis as can be achieved in this age of rapid technological progress. Despite being the species that builds wonders and improves our overall situation at a breakneck pace, we are also the species that loathes any and all change. It is the human condition to be unhappy at the prospect of vastly beneficial progress - because it will upset the mundane routines of our lives.
Over at Depressed Metabolism, you'll find some thoughts along these lines applied to cryonics. Why has cryonic preservation of the fine structure of the brain remained an unpopular option over the decades since its invention? Everyone and their dog has an opinion on that topic, but this one focuses on fear of the future - a form of distaste for change.
One reason why advocates of cryonics are not successful in identifying the cause of its limited popularity may be that they are inclined to exempt cryonics as such from its explanations. The assumption is that cryonics as such is a good idea but technical or practical problems prevent its widespread acceptance. But there is a major problem at the heart of cryonics itself. Many people have little difficulty recognizing that cryonics requires a person to choose to be resuscitated in a far and unknown future. In a sense, this property of cryonics is more about being "reborn" than about "extending life": Humans have evolved to want to survive but this instinct does not appear to assert itself when faced with the choice to go into biostatis in anticipation of resuscitation in a far and unknown future.
Little change is more radical than that which will be experienced by a revived cryonics patient: possibly a century removed in time, with a newly manufactured body, new society, new life. Starting over with next to nothing after a journey to an unfamiliar land, in other words. We've all done this at least once, but that doesn't mean it's an appetizing prospect in the later years of life - no matter how well understood and accepted intellectually, the grumbling ape that lives within us all is not going to like it.
In this sense, signing up for cryonics and following through with cryopreservation is yet another in the long list of battles we have to fight with our base nature. Day in and day out we wrestle with the ape within so as to be somewhat better than our instincts alone would make us. It is a noble war, for all that it generally goes poorly from moment to moment in vast majority of folk.