Solid state drives are based on flash memory, which age very differently than standard spinning platterplatter-based hard drives. Each sector has a limited number of write cycleswrite cycles, so the drives include wear-levelingwear-leveling features that allows the drive to last longer by essentially fragmenting the drive on purpose.
The read times are not greatly improved by defragmenting as they are in standard drives, so there is no real gain in defragmentation, but by doing so, you are increasing the number of writes to the drive, thereby decreasing the drive life.