The one thing that happens with the subscription is that once one person upgrades everyone has to follow suit or they can't read newer version Models / drawings etc
Other 3D formats don't share all the Solidworks features.
You also get no native Solidworks drawings so have to either redraw or use a DXF/DWG
Customers get annoyed when they have the latest version and then have to mess about converting files to another 3D format.
They also get annoyed when they get charged extra because time has to be spent converting the 3D format into a usable Model/Drawing
It doesn't play out quite like that in reality. Yes you make lots of valid points of what could be a problem on flip side there are many valid points of why not having native files on the same release makes little difference and in some situations is a major positive.
With a step/parasolid/iges etc it's literally one click to open the same as opening a native file. A parasolid from Solidworks opens in another soildworks exactly as it was in the first Solidworks without the history. This goes for an assembly to.
Now say a parasolid file assembly is 50mb the original Solidworks files assembly may be getting towards half a gig in size. So it takes forever to download. Then you get the Solidworks assembly after spend hours downloading it and need to do some modifications - you will need to spend time looking at how things are driven off each other and how things were constructed. The whole thing may fall apart by simply altering the diameter on a hole.
Flip to the parasolid you just imported instead and you need to move a face, simple click move distance and you have zero problems - nothing falls over.
I could write a book on the positives and negatives on both sides, but really it's in the software resellers interest to make out it's a really bad thing if clients (a) have different software (b) the software isn't the latest release. The reality is far from that.
It comes in as a solid model or surfaces with no history. But here is the thing what would happen if you had a system with no history? Plenty out there and they do just a fine job. Now if you look at a model and have had only training in how to use the parametric history it can seem impossible to do anything with these dumb models, this couldn't be further from the truth.