The rate of bugs users experience in a system declines proportionately with use.

Each touch of the system is a time where a user could leave and never return, or file a bug that is fixed.

In the former case, the system now has one fewer user, so less energy that might fix the bug… but also less likely that bug is experienced.

In the latter case, the bug gets fixed, and is now improved for all future interactions.

Even a small chance of leaving or filing a bug that actually gets better, but every touch has that tendency, so if the functionality stays the same it gets better.