If you always wondered why you would put a sata ssd with it's own enclosure inside of *another* enclosure to use it as a usb drive... well there are reasons, as additional armor is always nice and early sata ssds could get warmer than today's. If you break the sata leads on the ssd, well you have a whole lot more of a mess than if you break the extra usb port on the enclosure. That is for sure. But really, it is pretty safe to just connect this directly to the sata ssd these days, as they are very light and the sata connector is not going to be too terribly stressed. This is also workable with hdds, though you should be a bit more careful as an hdd obviously has some more heft to it and are more sensitive to dropping or stressing the sata port. Still not a really big deal.
This works great with the Rapsberry Pi 4 that can boot from sata, or just if you want to have a big /home volume. Going from sd card to sata on the PI is like going from hdd to ssd, well worth it.