Because just like the stock market, some people are more psychologically 'resistant' to short term swings in price. Until one can train their mind to be more long term thinking, it is easy to look at the price hour by hour, day after day and worrya bout what will happen next.
That said, one needs to keep informed so that if 'it hits the fan' then they can get out before it gets too ugly (like when a company or the currency might start to fail and loses long term viability, but even then it is a gamble, if you buy when its cheap, you can lose all, or gain a lot if it recovers).