[AdamH12113]

An RTC really needs a battery, and even a smaller battery like a 1220 takes up a fair bit of board space -- space that could be used for another connector or more functionality. And even if you have an RTC, you still have to handle the edge case where the battery dies or is removed and the clock resets. Critical low-level internet services probably shouldn't require clients to already have the correct time.

I use an external RTC with a Raspberry Pi for some sensor systems I work with. Its purpose is to give a reasonable chance of having the correct time for recording data in remote locations where no internet connection is available at startup. For a Pi that only provides network services (and thus always needs a working internet connection), I probably wouldn't think to bother.