That's an evolutionary effect based on subconscious instinct. If other women have accepted a male, he is more likely to be viable for mating. A loner is likely alone for a reason. Women naturally don't trust their own decision-making, and that's an evolutionary effect based on social norms over the past few millennium of male domination.
Truth is, you can overcome those instincts with knowledge and being self aware. However, since most people are stupid, they never will, and they will lie on a poll such as this because they are also under the illusion that they are their own independent thinker, when in reality, most of them are told what they should think by TV (one of those things being that they are independent thinkers).