The whole idea behind rational self-interest is that the individual does not consciously seek to make themselves worse off. That doesn t mean that people don t make bad choices. The idea is that the rational person weighs the cost versus the benefit and chooses something, based on what they know at the time, that they believe is the best for them. Rational self-interest does not mean that we do not care for the welfare of others. It does mean that we choose to care for others when the cost to ourselves is lower.
Economic choice involves changes to the existing state.
A person only changes their existing state if they believe that the marginal benefit will exceed the marginal cost of the change. Choice requires time and information. Time and information are scarce and valuable. How much time and information a person will expend in trying to make a decision is determined by benefit versus cost. A person will continue to research as long as the expected benefit exceeds the expected cost of using time and information.