The venue is necessarily a centralizing agent, whereas airlines necessarily have to use decentralized agents (or did when GDS was invented). The decentralizing of event tickets is artificial.
There isn't a lot of obvious utility in allowing anyone in the world to buy a concert ticket (unless you want speculative resellers in your ecosystem). For people travelling to an event, that's what the will-call window is for, and it requires a matching ID. Whereas airlines cannot reasonably maintain a network capable of selling a ticket to anyone worldwide despite their being a very good set of reasons for that to happen.
This probably also explains why airlines allow independent agents, but no reselling. The original market (pre-internet) required it, but the airlines didn't really want to sacrifice their margin to speculative resellers (scalpers).
Concerts used to be sold in a centralized way (you could buy tickets to a specific show at one of a few authorized venues, in person). This worked fine before the internet, since it meant that fans stood on equal footing with speculative resellers. If I want to scalp tickets, I have to go stand in the rain with the fans, and I can't buy 50 tickets since the sellers won't sell more than a few at a time.
Contextualized with how the different industries were created, we can see why GDS made sense at one point, but doesn't really anymore, and why it would never make sense for event ticketing.