The answer is simple, people place subjective value on things for many reasons including "because it was tuesday". People collect all sorts of things like stamps and old coins that have no direct monetary value today, who wants an old used stamp, well in some cases they are selling for a lot of money. Try to stop thinking of things as televisions and mobile phones, sometimes even a flower can be sold for something. Freedom is priceless 
you simple anser doesn't convince me. stamps and old coins have a nostalgic value which can explain how they start to gain monetary value.
Good point, but why would we place value on something nostalgic?
Without getting too philosophical, the simple answer was really a reference to specific aspects of motivators in random chaos theory.
http://www.becauseitstuesday.com/
https://www.facebook.com/BecauseItsTuesday
"Random Acts of Kindness Just Because Its Tuesday"
Trying to understand "why" people do things, and why they choose to place subjective value on something, is an impossible task. This is because people are random beings, and do random things. Something can be given value "just because", and that is the answer.
Bitcoin represents "Freedom" of choice, and to some people that is attractive. We tend to place value on things that are attractive.
Hope that clarifies my post
