I'm almost positive there are no more than one or two people (at most) at Bobcad that were around when V21 was new and I'm pretty sure they don't support it. Not really surprising, my youngest was still in diapers back then and is now attending RIT.

If your machining needs haven't changed since you bought V21, it's pretty hard to criticize sticking with it so long as it keeps working. Personally, the things I get asked to cut get more and more complicated while those designing the components continue to push the boundaries of what can realistically be produced. On top of that, 3d printing has raised those expectations even further. In an environment such as that, you have to stay reasonably current on the software end just to keep up with expectations. In my opinion, that is the main reason to update and not everyone faces those problems.