There are too many choices, which naturally gives people a sense of "cheapness" and makes them feel that they are not worth cherishing. People tend to value things that are scarce, even if they are not useful. As endless as human desires are, when faced with real options, people tend to choose only based on real needs. Each additional choice equals a large increase in information processing, and when there is too much information people will avoid comparative analysis and do things based on their feelings, choosing one or two at random. There are too many choices, and sometimes there is a phobia of choice. The fable "Brittain's Donkey", just two piles of grass, because it is impossible to judge which pile is more, which pile should be eaten first, and even starve themselves to death, which is also considered to be the best of donkeys. The choice here refers to products of the same kind. There are many products of the same kind, and when there is serious homogenization, the demand will be reduced. If it is a different class of products, there is no such situation. With free samples, most people can't be bothered to try them all, which is probably the most fundamental reason for only tasting 1-2. Of course, if the instructions for the jam had indicated a significant difference, one would have tasted more than one.