My theory is that people buy it as holiday gifts.
I think when the beginning of the year bitcoin will experience a strong enough push, because the turn of the year is a very surprising moment.
2012 - $4
2013 - $65
2014 - $200
2015 - $185
2016 - $365
2017 - $780
2018 - $3200
Puts a lot into perspective.
like the thread above, explaining when the beginning of the year will tend to increase compared to the previous year