Every one seems to be giving examples of why one might want to use a door with no jamb. But I think the point is that a computer programe should never be able to dictate what designer wants to do. There are millions of designers out there in a multitude of differing fields, so there is just no way that any of us (nemetschek included) can possibly begin to guess at how every one might want to use this programe, or the tools that it provides.
There for I think it's Nemetschek responsibility to provide an application with the absolute minimum of these little bugs that could either dictate design to us, or make it difficult to produce that which we can imagine.
That's my pennies worth...