The NVRAM is primarily intended as a debugging tool for developers.
The real-time clock can be used by filesystem/mass storage ROMs to set the correct file creation or modification dates.
All Nova cards come with the 32KB chip. [https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/nova-nvram-rtc-for-amstrad-cpc-latest-news-from-pulkotronics/msg205606/#msg205606 Source]