Why you should not follow the crowd?

Under the effect of peer pressure, many people can blend in with the larger crowd without questioning their own actions. The result might be a large group of people following the few ones who started the wrong trend.

Successful people are always the minority of every group. If a person followed the footsteps of the general public then they are very likely to end up with average results.

Most people are unhappy and not satisfied with their lives. When a person follows the crowd they might end up with the same happiness levels of the general public or even lower.

Each person has their own unique needs that they must satisfy in order to be happy. If a person follows the crowd then they most likely won't satisfy their specific needs and might end up feeling unhappy.

In many cases groupthink was found to lead to many wrong decisions as people try to match the opinion of the majority to blend in.

According to social proof theory, people look for others for guidance when they don't know what to do. If a person found so many people agreeing on an opinion then they might automatically support that opinion without questioning it. (See Why do humans join groups?)

Inside groups, most members will stick to their comfort zones and prevent themselves from trying anything new. This might force the whole group to miss many opportunities.

When a person tries something different, the members of the group might quickly scare them in order for them to act like the group. The members of the group do this out of fear.

Some studies have shown that groups of people can do irrational things while each individual member would still think that they are doing the right thing because the whole group is doing it.

Negative beliefs can diffuse fast through a group and infect all the members. A new comer can easily acquire the false beliefs and then consider them facts. (See Why are some people very pessimistic?)

According to Wikipedia, groupthink is a phenomenon that occurs within groups where the desire for harmony and belonging can make people think irrationally and do irrational things.