Well, yes. I suppose ultimately it is money. Only Fox (and to a limited extent Disney) seem to support Seamless Branching (Beauty and the Beast couldn't support it, as it was using the angle feature for the WIP version - I'm hoping this years Lion King will use true seamless branching like their...
It's not to save money. It's becuase no European authoring house can do seamless branching properly. True seamless branching is a very complex art. There's a thread where I posted everything I know about seamless branching (and no one's disputed any of it) but it involves the same technology...