Exchanges match buyers and sellers. Supply and demand creates the current market price. As demand increases over available supply the price increases , as the price increases this
Tempts investors to spend or sell their Bitcoin
Increases the total value that needs to flow into Bitcoin to offset inflation. Since inflation is currently 6.25 btc per block x ~144 blocks in a day (~900 BTC a day mined) this means that when bitcoin reaches 100k usd per btc there needs to be ~90 million usd a day in inflows to Bitcoin to offset inflation to secure the network
Thus you can see that there will always be buyers and sellers