The other answers are hinting at it, but Optane was fundamentally much much lower latency than NAND flash used in SSDs.

SSDs use lots of tricks to hide this latency (using RAM). However, when the data is super critical, you can't just throw some data in RAM and hope that it gets written out.

Enterprise flash drives have battery backups and keep the system alive for a moment to flush out the writes, but Optane doesn't need special tricks to get this sort of durability, it just has it. The Optane can keep accepting writes, eventually the RAM of the SSD is filled, and then the write performance falls off a cliff. However, if your workload gives the storage device a breather to write out to flash, you wouldn't notice the difference.

If you have a large stream of critical data flowing in that has to be stored and can't be lost- Optane suddenly looks way better than SSDs