Yes, I understand that, however a solution can (and hopefully will) be implemented. For example if I upload the same video in Facebook, Facebook automatically converts the video so that it plays back in any browser. Users are used to this, and our Mac-based members don't understand why they can upload a video in a Facebook group but can't upload that same video in our Invision Community.
My understanding is that that is something that Invision already does for the Gallery, so hopefully that feature will be added to the forum as well in the not-too-distant future. I remember discussing this with Charles during a Live Topic last year.