Bitcoin is the mother currency of all the coins and if we relate this in our real life example with our family mother has more value than anyone in our family so the concept behind this was established in 2009 and first the mother came as the name of BITCOIN and then after their children came with the name of ALT-COINS so i think there is highest value of bitcoin.

Furthermore, the second reason behind the highest value of bitcoin as it was established in 2009 and the value for bitcoin was 0.20$ and due to low market cap it has only 21 million of supply and it is at the 1st rank where no other decentralize coins were in market so the total investment was at one coin name bitcoin and the price increased like it was happen before to the gold.

Nest reason for the highest value of the bitcoin is all ICO and other tokens where under one cryptocurrency before 2 years now a days ETH is very know for the same as it is the follower of bitcoin and due to most ICO and tokens under bitcoin to join this ICO we need to buy bitcoins and if the project was good everyone was likely to invest and the price was increased and today it is at 1st rank of market cap.