“This seems to be the minimum recommended to the latest Raspberry Pi desktop which can easily eat up more than 8GB space. And if you add that it is best if you leave about 50% free disk for the longevity of the card, then 16GB is simply not enough.
hdparm -Tt /dev/
Timing cached reads: 196.41 MB/sec
Timing buffered disk reads: 21.96 MB/sec
(on a Raspberry Pi Zero)”