I could imagine that licensees for music in games ask for so wide a range of use cases and possible future distribution channels to be included in the licence,

I could imagine that licensees for music in games ask for so wide a range of use cases and possible future distribution channels to be included in the licence, that licensors are genuinely scared that a forever grant would be almost like completely handing over the copyright. Licensees will want distribution over every future steam competitor, at any price point, in any form of package deal, remaster version, mod remix. Add gameplay videos and cloud gaming services, all far outside control of the original licencee, and the rights holder will find it almost indistinguishable from granting infinite transitive sub-licensing.