Many years ago I spent a couple of weeks fixing a firmware bug. The firmware was only a few dozen bytes shy of the EEPROM. I just #ifdef'd out a bunch of features to focus on debugging what was broken, but to get the fix released I had to manually optimize several other parts of the code to get everything to fit in the 2MB or whatever it was.

Would've been nice if someone had reserved some space ahead of time. Maybe they did, but nobody was around who remembered that codebase.