Yes, people behave stupid. That's why we have ponzi-like schemes and market bubbles. But that's off topic. Here we talk about the fact that by holding bitcoin you own nothing. Regardless if price of a particular stock is hundred times above it's real value that fact won't change. And of course, marketcap of bitcoin is the stupidest concept in this whole fantasy kingdom. There's zero capital owned by bitcoin holders, so zero shares in capital multiplied by markt price gives zero.
Let's say what you just said was true for a moment. What's your solution? You expect everybody to sell their bitcoins? As you see it is not collapsing but getting only bigger.
Here is a good reason which'll make you buy: Just participate so you can also make money. You don't even have to buy a "whole" bitcoin to participate. You can use 1% of your wealth. Dump it when it becomes 2%. You will be risking only 1% of your total wealth.
No matter how many times you scream that "crypto has no value", "it is worthless" bla bla bla, the markets don't give af. The price tag for a coin is still $42k. You can either join, or you can cry all you want. Nobody really cares. If you are so sure about that crypto has no value, why don't you short it anyway?
Have fun staying poor.