Because people assign value to it. Its exactly the same as Baseball cards (or any collectibles), old cars and diamonds. To some people that stuff is straight up dumb and to others super valuable. The items themselves arent by nature valuable to everyone.
I can't grasp that concept. I'm a numismatist and somewhat of an American history guy.
The original coinage of the the US starting in 1793 had a high ratio of intrinsic value ( call it metallic content ), relative to face value , so you had a good chunk of faith with the copper, silver, and gold in the coin.
The mint could not produce enough coinage for commerce in the early years, up until the civil war was over. What sufficed as coinage was a hodgepodge of European ( mostly English and Spanish coins ), some American stuff, and some bartering in order to do business.
The dollar gained faith and trust over the centuries, FDR kinda fucked that up circa 1933 with Gold, but our coins still were silver until 1964.
Point is there is history to back the the US dollar, I see nothing behind Bitcoin !
Say I'm old fashioned and over the hill, but I will not touch BTC