PCBgogo

I was just wondering why people (users and programmers) insist on cramming all information into one model (schematic)? A logical schematic would be a complete schematic that would be required to understand the circuit.
A physical schematic would be based on the logical schematic but with additions/changes of how it is manufactured.
For instance an audio preamp logical schematic has a pot to adjust the gain. In the physical schematic that pot would be connected through a header and some (shielded) wires because it is somewhere on the front of the case. 
Other physical aspects could be, differential signal length rules, how parts of the logical schematic are split up over multiple PCB boards, details on how plugs and sockets are connected to the PCBs (like the pot example), annotations on how much current or voltage a specific net may have to cope with, etc. That sort of thing.
Ideally the CAD software package would keep these two schematics in sync and have rules to check for errors, similar to how currently schematic and PCB is kept in sync.
My question is why this is not so. I see schematics that have a bit of both - but usually not all physical aspects are noted/documented. The person laying out the PCB has to know/remember that these high-speed differential pairs should be equal length, or that the PCB layout has to use a tree layout (or whatever it is they use for high-speed RAM)... 
The physical aspects clutter/obscure the functionality of the circuit, but are part of a whole design. 
In software for instance, it is common to have logical and physical models, for instance a logica Data Model abstract the details on Relations, the physical model is what is in the database exactly. There are multiple views of a software design that can be used to express/document it on paper.
Makes sense?