Too many options reduce the likelihood of deciding.
More options should mean a better chance of finding the ideal one. In practice, past a certain point, a bigger catalog reduces both the likelihood of buying and satisfaction with whatever ends up being chosen.
A supermarket set up a jam-tasting booth. At some points in the day it displayed 24 different flavors, and at others, only 6. The 24-flavor booth attracted more people to taste, but only 3% of tasters ended up buying a jar. At the 6-flavor booth, far fewer people stopped to taste, but 30% of them bought one, ten times more than with the larger selection.
Comparing many options against each other requires real cognitive effort, and that effort produces decision fatigue. Faced with too many alternatives, many people opt not to decide at all, rather than risk choosing badly among so many.
Source: Iyengar, S. S. & Lepper, M. R. (2000). When Choice is Demotivating: Can One Desire Too Much of a Good Thing? Journal of Personality and Social Psychology, 79(6), 995-1006.
Narrowing a catalog, a menu, or a form's fields down to a curated number of options usually increases conversion more than adding a new alternative "just in case" someone needs it.
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