You don't know if there is no party that controls 51% as BTC ownership is impossible to verify. One can have 100 wallets, or a few people can work together.
That's the worst case scenario. Since you need at least $30 billion ++ to coordinate such an attack. Very very few people have the capability to do it or will risk doing so and face prosecution when they are already billionaires in the first place. You seem to be super persimistic. Anything can happen in worse case scenarios. Amazon or other stocks can go bankrupt etc. That's why you have trade and manage your risk. Anyone can go outside and be struck by lightning and die, that doesn't stop me from going out to enjoy life.
Bitcoin is a great store of value, sure... Until the power goes out. No electricity, no value. So now you are back to the problem of extending bitcoin credit with the hope the power comes back on so they can repay you the bitcoin loans. Meanwhile, gold has been sitting there all along going, "Ohhh, OOH! Me me me! I'm still here!"
I don't know what era you were born in. But it sounds like I am talking to someone who was living in the time of wagons and horses
The first thing is to understand what the risk is. The risk that Amazon will drop more than 80% in less then a year is close to zero. For the bitcoin that risk was real as it happened. If you cannot make a realistic estimation of the real risk you are surely not able to manage that risk, as you don't even understand/know the risk. I don't know anybody who got struck by lightning and died, but I know quite a few people who lost money in bitcoins. So there the risk of an event happening is completely different too. I choose not to invest in bitcoins but to (continue, as I was trading before the bitcoin was created) trade futures. I am sure that my profits are far beyond the average profit that "average joe" made with his bitcoins. If bitcoin is considered as a currency then it will be one of the weak currencies as it lost in less than one year 80% of it value. It belongs in the category of: Iran rials Vietnam dongs Sao tome dobra Indonesia rupiah Belarus roubles Laos kips Guinea frans Zambian kwacha ... https://www.therichest.com/rich-list/poorest-list/the-worlds-15-most-worthless-currencies/
This is applicable to credit and debit cards and interbank money transfers also. Do you plan to come to the grocery store with 100 oz gold bar?