Here's why:

* Lunar Cycle: The moon's phases are part of a cycle that takes approximately 29.5 days to complete.

* Gradual Change: The moon's appearance changes gradually throughout this cycle, progressing from New Moon to Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent.

* Daily Shift: Each phase is visible for a few nights, and the specific time of moonrise and moonset shifts slightly each night.

So, while the moon does change slightly every night, it's not always a noticeable change. You'll see more dramatic differences in the moon's appearance every few days.