People don't used to trust in new things or in things that they don't know. Moreover when people discover a new technology most of time it's thanks to the medias and we all know how the media can be idiots about the informations they gave to people. I speak about this but are you sure that "people fear about bitcoin" ? I am not sure
About people who understand the technology they can be afraid of the vollatility, afraid to lost what they have so they prefer to not invest.
Pretty much this. Most people don't have a good understanding of technology and only take away a few bits and pieces and unfortunately the media sound bites tend to stick. 'Exchange hacked!' 'Bitcoin + Darkweb!' couple that with the volatility compared to the investments they are used to and the numbers they are doing in their head equate bitcoin to dark sorcery.
Over time we will see more people becoming educated and understanding the actual strengths and weakness of the various crypto currencies.