Bitcoin is the first coin that started crypto currencies. It has always been the coin you purchased to come into crypto and then traded for something else on the exchanges. You couldn't invest money and then trade for the coins. You had to purchase Bitcoin for any transactions to happen. The same is when you sell any of your alts you have to sell them to Bitcoin or Etherium to move out of the exchange.
Bitcoin is down from $22 500 in January to around $6500 currently and is expected to turn and reverse the downward trend. The smart move is to have Bitcoin right now as that is always the first coin to climb. Others follow and copy what it does.
If you are holding bitcoin and it starts an upward movement you can gain an immediate 15 to 20 percent by holding this coin. There is expected to be a lot of interest this time from larger corporations and finance institutions who are waiting to invest. Once the coin starts to climb it is hard to catch it up so it will be interesting to watch.