There are: https://nimbusdata.com/products/exadrive/specifications/

They are just not listed in shops for poor people. (joking)

I just addressed that in a post above yours.

https://lemmy.world/comment/17434700

Basically, smaller form factors are probably just better in this case. 3.5" drive bays were designed with more complicated mechanical drives in mind, and given how nand flash memory works, they don't make as much sense for SSDs.