I feel like the hard drive should be self evident, but I wouldn’t hate a used SSD so long as it’s a modern drive for a discount. With SSD prices always falling it would need to be compelling though.

Same reason why people prefer getting a new car to a used car: you don’t know the care and maintenance, or wear and tear, the previous owner maintained. You could end up saving money… Or you might end up buying a junker.

Flash technology used in SSDs has a limited lifetime in terms of writes per location. Although SSDs have the intrinsic feature of wear leveling to attempt to spread out those writes across all locations in the device, eventually one or more locations will wear out and no longer accept data.

As there is no easy way to determine how many write cycles have occurred in an SSD prior to purchase, there is always a risk of getting a device that starts failing the day after one installs it.

Lifespan already got eaten up. Higher rate of data loss.