If tickets are selling themselves, why do they have to mention it every time? It sounds like amateurish marketing...
Quite the opposite. It's a promoter's job to build the most buzz possible about an event. Creating (and reinforcing) the image that every GGG fight is an event that fans want to see helps build momentum for it. The best promoters feed that hype every step of the way to get fans excited for it and convince those on the fence to buy in. The environment is the selling point in an era when we can all get better views just watching on TV. Even critics of GGG or K2 have to admit they market the hell out of Golovkin. Alot of blue chip fighters would benefit from the same approach.
Every promoter, every salesman, does the same thing. It's a crude, simple marketing trick but it isn't amateurish at all.
It feels amateurish because they do it so predictably, even vs. completely unknown opponents like Wade. I can't recall Floyd issuing press releasing that "half his tickets were sold".