I do data recovery for a living and SSDs fail especially Sandforce based ones like Apple has been using lately so I'm very interested in being able to replace one without having to replace the logic board -- especially after the machine is out of warranty. If I can't, this will mean selling the machine as soon as 3 years is up instead of being able to hand it down to a family member or friend.
The other thing is that one will need to decide from the get go how much space they would ever potentially need in the machine if they can never increase storage. I have many clients who made mistakes when purchasing newer Apple laptops and Mac Minis thinking they would be able to eventually upgrade RAM and/or storage.
Additionally, I guess I'm old fashioned but a machine called Pro should allow for some upgradeability.