Fragmentation is one of the main ways Solid State storage is as fast as it is, parallel access to a file across multiple (usually 8) NAND chips.
On a spinning drive, fragmentation is a fact of life, and while different FS have different rates, it is not absent from any.
Another big benefit from a good defrag program is the ability to selectively place files on the platter(s), having the most frequently accessed files on the outside and moving to the least accessed (and bulk storage) on the inside, you will see 50-300 percent better disk performance. For example, one of my WD Blue 1TB (WD10EZEX, single 1TB platter, one of thefastest drives aavailable) pushes 208MB/s on tthe outside going down to 133MB/s on the inside.
Never ever defrag an SSD!