Not the original commenter, but possibly because SSDs are eventually volatile.

SSDs store data by trapping electrons in cells to represent your ones and zeroes, and when the disk is unpowered those electrons can eventually escape, causing data loss.

This may take years to happen though, so if you use the disk frequently you are unlikely to experience it.

That said, the time to unpowered data loss gets worse the more cumulative data you have written to the disk over its life. SSDs that are extremely badly worn out could lose data in months, not years.

Traditional spinning disks don’t have this issue as the magnetic storage doesn’t depend on power to stay magnetised, so it’s a better choice for archival storage.