Reduced test cases make it way easier to figure out what the actual bug is. E.g. a real world example is when I tested a "slugify" function with hypothesis. It almost immediately spat out this failing test case:

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaẞ

Boy I sure do wonder what character could possibly be causing issues there. whereas without shrinking it might instead spit out something like

ЁЂЃЄЅІЇЈЉЊЋЌЍЎЏАБВГДẞЕЖЗИЙКЛМНОПРСТУФХЦЧШЩЪЫЬЭЮЯабвгдежзийклмноп

Which makes finding the offending character a lot harder.