I can see why someone might get the wrong idea - there's nothing immediately obvious on the home page which states that the Mac version of
Media Center only supports audio at this time.
As for why someone could
buy Media Center for Mac without trying it first - perhaps they have already tried MC on Windows, or been recommended it by a Windows user that doesn't know the two are completely different products right now.
I'm hesitant to comment at all since this is what got me banned last time, but with a lot of software I've recommended to people, I have found that they're far less likely to give it a fair chance if they're using a trial rather than having bought a license.
As soon as something happens that they don't like, or it doesn't behave in a way they expect, it's over.
If I tell someone to try Media Center, there's a good chance they'll come back to me and say something along the lines of "this is too complicated" and abandon it - no matter how much I protest, or offer to help solve their issue.
They don't realize that Media Center is not like iTunes where there's only one way of doing things and if you don't like it, you're out of luck.
If I convince someone to
buy Media Center first, they're a lot more willing to spend the time required to get over that initial learning curve, at which point they're probably a JRiver customer for life, because they can see just how powerful Media Center is.
There's a wide range of products that use similar, but far less flexible licensing than JRiver. Until recently, the same was true of all Adobe products, for example.
It has always been a nominal fee ($5) to switch your license from Windows to Mac or vice-versa. They void your license and mail you a new disc - I've done this a couple of times. (moving to Mac, and back to Windows now)
I know, because I have separate licenses for my Mac and Windows copies of Lightroom and Creative Suite 5.5.
Lightroom has always had a multi-platform license - since v1.
They only changed it with the current Creative Cloud (or maybe CS6, which I didn't get)
This is true of their pro applications, but not their "consumer" ones, which I believe have always been cross-platform.
I don't feel like digging up a huge list of similar pro-apps, but this is certainly not uncommon (if the apps even are cross platform).
I would say it's
only common with professional applications, and quite rare today. These companies generally have feature parity across both versions, and allow you to switch without much difficulty.
The reason is that the separate licensing is the reason there is a Mac version of MC. Without the users who want to use it on OSX paying for the separate development, somehow, there would be no way to fund the additional development effort required to produce and improve the Mac version. Over time, as the development progresses and the Mac version reaches parity, perhaps this pressure will lessen and changes can be made.
Generally, that's not how I've seen things done. Until there is feature parity - or at least 90% of the way there, the developers normally charge a reduced price - if they charge anything at all until it's done. (often they have a "closed" beta where you can apply and get access within a week) Sales pay for the development costs after the fact, rather than during.
Don't get me wrong, I completely understand why the JRiver team does it this way - especially due to the way they handle development of each new version (building it up over time, rather than saying "here are X new features, that's v19 done") but it's not what people expect these days, so I can see why someone might hear how good "JRiver Media Center" is and simply buy a license for their Mac - without knowing that it lacks much of the functionality that the Windows version has.
The inflexibility of the license with regard to platforms - no way to switch, and no discounts if you already own Media Center on another platform is rare these days, and a bad deal for consumers -
especially when you consider that there is no interoperability between versions. If you move to v19 on Windows, you are
required to buy a v19 license for Mac and Linux too.
Not even Adobe does that. If an image was edited in a different version of Camera RAW than you are currently using, for example, you will still be able to view all the changes and it will be rendered correctly - you just won't be able to edit it on an older version without dropping down to that level. I know this because I stay up-to-date with Lightroom, but not Photoshop. (there is no way I will pay a subscription for access to software with Creative Cloud)