Perhaps you mean Enterprise storage versus Desktop storage?
Reasons are here.
The most important difference is regarding management and service.
Now to the hardware.
In the past the SCSI disks for servers had visibly more electronic circuits than the ATA disks for the desktop. And Unix desktops aka workstations had SCSI disks. The last Sun workstations used ATA disks...
Meanwhile the higher integration hides the complexity, and the price gap between SAS and SATA disks should heavily shrink - but does not. It might be the sales strategy of the big manufactures, or even a cartel...