There are thousands of different investments and investment strategies to choose from but the average investor does not have the time to familiarize themselves, let alone properly evaluate each one. Humans are constrained by what economist and psychologist Herbert Simon called, "bounded rationality." This theory states that a human will make decisions based on the limited knowledge they can accumulate. Instead of making the most efficient decision, they'll make the most satisfactory decision.
Because of these limitations, investors tend to consider only investments that come to their attention through websites, financial media, friends and family, or other sources outside of their own research.
Perceived familiarity and the comfort associated with that isn't likely as valuable as one might think. This concept can have overlap with our overconfidence bias.
Having a disciplined steward to systematically implement a custom investment plan is the best way to avoid our emotional and behavioral tendencies.