Lots of consumer SATA SSDs don't have any thermal pads between the PCB and the case, and plastic cases are common. Heat just isn't a problem for a drive that's only drawing 2-3W under load.

And most consumer NVMe SSDs don't need any extra cooling for normal use cases, because consumer workloads only generate bursts of high-speed IO and don't sustain high power draw long enough for cooling to be a serious concern.

In the datacenter space where it is actually reasonable to expect drives to be busy around the clock, nobody's been trying to get away with passive cooling even for SATA SSDs.