You might consider a Basquiat to be worthless and I would agree with you. But there are enough people and institutions who see something in it that we don't.
And that basically sums it up with Bitcoin. There are enough people who see something in it that you don't.
For me, I see it as an opportunity to store money outside of the monetary system. Private money if you will. Now that cash is in decline and online transactions are increasing (in Sweden 'no cash signs' are emerging) then all of my money is under the control of central authorities.
This would be fine if you could 100% trust these authorities, but considering the bank bailouts, pension raids, money printing, economic policies, continuing fraud and manipulation, having an option outside the monetary system to store
some money is a great idea.
The Bitcoin blockchain has at max, space for 21m full units. To buy a full unit today it will cost near $11,000. That is because more and more people are availing of the option to store money outside the system. For sure, it is volatile and risky, but all that does is limit the amount you are willing to purchase. In fact, the volatility can act as a deterrent to spending sums that you are not prepared to lose, or will adversely impact your standard of living if price crashes.
If economies prosper, productivity increases, wealth is distributed and trust returns to the banking economy, Bitcoin price will crash.
But as long as mistrust prevails, phoney QE programs are applied, pension raids occurring, bank charges, bank manipulation, bailouts, write downs for developers but not mortgage holders, write downs for vulture funds but not home owners, bogus selling practices, money laundering, criminal activity, outlandish bonuses, little to zero accountability, etc...etc..
As long as US and major economies of the world continue to drive up debt and devalue their currencies then the option for the ordinary joe to put money outside that system will prevail.
It's a brilliant idea, not without its flaws, problems and risks. But clearly people see something in it that you don't and in turn place value on it.