I have just opposite opinion on this, many buy cuz they know it will be bitcoin to bitcoin gold ratio 1:1 like with bitcoin cash.
They hope that with this they can earn some free money and that they will have some more bitcoin after this.
Price movement is small and for the moment expect, 6000 will be broken after this fork.
The main reason for the increase is the easy money factor and this split wont make any drastic changes in the price of bitcoin ,the price has already crossed the $6000 valuation and reached another milestone for the day but would like to see whether it will stay above this valuation for a longer period or we would see a correction after the bitcoin gold fork or at the next fork and that is the million dollar question,will it keep on rising till the next fork or not,it is really hard to predict .