Your computer will not freeze if your input is small enough no matter what big-O says. In many cases it's guaranteed to be small or small-ish.
And in many cases it's assumed to be small, but not guaranteed. That's where the trouble lies.
A classic example is Windows using a quadratic algorithm for arranging desktop icons that caused severe performance issues when users had many icons on their desktop.
https://github.com/microsoft/Windows-Dev-Performance/issues/...