Mänsklig psykologi. Vi är flock- och vanedjur. Livrädda för att göra fel. Då kommer vi välja det som känns bra.
Du kan ju kolla på ARKK också, har gått jättefint senaste året 
Lite olika bias som drabbar investerarar och i synnerhet denna:
Chasing Trends
This is arguably the strongest trading bias. Researchers in behavioral finance found that 39% of all new money committed to mutual funds went into the 10% of funds with the best performance the prior year.5 Although financial products often include the disclaimer that “past performance is not indicative of future results,” retail traders still believe they can predict the future by studying the past.
Humans have an extraordinary talent for detecting patterns and when they find them, they believe in their validity. When they find a pattern, they act on it but often that pattern is already priced in. Even if a pattern is found, the market is far more random than most traders care to admit. The University of California study found that investors who weighted their decisions on past performance were often the poorest performing when compared to others.How to Avoid This Bias
If you identify a trend, it’s likely that the market identified and exploited it long before you. You run the risk of buying at the highs - a trade put on just in time to watch the stock retreat in value. If you want to exploit an inefficiency, take the Warren Buffett approach; buy when others are fearful and sell when they’re confident. Following the herd rarely produces large-scale gains.