We are spending years arguing about the price of Bitcoin, However the real output is finally conclude that Bitcoin is the only asset where you aren't forced to trust a third party to guard your own labor.
There are literally
thousands of investments like that. You can buy some rare diamonds and hide them in your house, or buy some bars or gold or buy some land. For that matter, you can buy any sort of tangible good and simply guard it with your own shotgun and you are not "forced to trust a third party".
Of course, 99% of people don't want to physically guard their life savings with one or more weapons (and even fewer are truly qualified to do so--and about zero can do it consistently). Most want to pay somebody else who is an expert at guarding stuff to guard their stuff. One type of institution that does this is called a "bank". Others are called, "brokers" or "financial institutions" and also "governments" who guard things like public records of ownership.
As for Bitcoin, most people invest in Bitcoin the same way they do other investments like stocks. It's just a name on a screen that they buy in hopes that its number goes up in the future so they can sell it and buy nicer things or live more comfortably.
Most people don't know that Coca Cola started as a cough syrup, and most people don't know (or care) about what started Bitcoin either.