It's not a matter of preference of less functionality or anything. It's a matter of money and time, if everyone (contractor, subcontractors, and consultants) could simultaneously upgrade to the most recent version, would be ideal. But doing this means an investment which is not to be taken lightly (Autodesk licenses are not cheap) and all companies; contractors, subcontractors, consultants, etc. have different capacities and employee number, and can't afford to make the investment simultaneously. Also, most of the times you are working with new subcontractors. So Scott, what you're saying while desireable, is far from reality.
And most of the times family creation almost always uses features that have been around for 3 years or more, not every single family requires or benefits from the new features. So it's not logical that Revit cannot rollback family files, it should be able to do it (at least for 2 previous platform release), and for the new features and parameters should be simply deleted from the family when rolling it back, as it already happens with autocad files.
Family creation is time consuming, if the content were easier to be distributed and created and encouraged,the more popular the platform would be.
It is an obtuse and narrow vision, (greedy?) from Autodesk's part not see this.
And for project files, It is comprehensible (I dare to even say, desireable) not being able to roll back. But here is where the coin turns for Autodesk, if families could be rolled back, the leverage to make users upgrade to the new version would be gone. So it appears Autodesk is not really focused on making work easier, but just into making it LOOK easier, so they sell more. Usually this is found out after the investment is done, that pisses people off. Every single Revit user and buyer I know has had this feeling once (even the ones I know that formerly were employed by Autodesk).
So please, tell your boss (or whichever responsible dept.) they really should consider only families to be able to roll back compatiblity to one or two older realeases.