You just replace the external and quite easily accessible drive ...
In my recent experience every serious storage is kept external: you want internal fast drive for OS and applications, and external huge redundant drives for storage.
Not all folks want to operate like that. A small-medium sized internal array is pretty nice for the immediate stuff you’re working on now, then have the big external stuff for backup/archive. I’ve had that setup in a few places and enjoy it.
what was the last time an external enclosure failed at you ?
In my case ........ NEVER.
Then enclosure it self? never happened to me either. I also haven’t had a computer fail on me such that I had to move all the internal disks to another computer (not that it would actually be hard anyway, especially on nice cases that allow easy hot-swapping). But ya know what, I can’t tell you how many drives I’ve swapped out. Opening up stuff will stay the same internal or external in that case. It just changes which thing you have to open.