Because people that already hold bitcoin will still be willing to buy. If you bought bitcoin at $1000 you might still be willing to buy at $8k as that would still price your avg bitcoin price at $4500 and won't be making a loss until bitcoin drops below $4500. Entry level doesnt mean your wealth but you being a first time buyer or entering into the bitcoin market at current prices. Which means when the price goes down you are going to make a loss.

It's not formally economically rational to be affected by history this way.

https://en.wikipedia.org/wiki/Sunk_cost

past performance is no indicator of future results.