I know it's possible to defragment a FAT32 volume, but is it a necessary practice? I'm asking because it feels like the read and write to SD card seems to become slower over time.
NO, I researched and it turns out defrag hurts sd cards. But maybe backup, format then save on it again may help?
After lot of writes, sd cards (like ssd) dies. If you recognize slower and slower functionality, change it before you lose data.