Because its different…and I know because I use to work for Chorus.
The fibre networks that are used for broadcasting are different to what you get your home broadband on.
These are specific circuits that are dedicated for television broadcasting. Not all racecourses have fibre broadcast connections. All the “main” tracks, the places that race often do - Avondale, Alex Park, Ellerslie, Te Rapa, Cambridge Awapuni, Manawatu Raceway, Trentham, Wanganui, Addington, Riccarton, Ascot off the top of my head have fibre circuits for broadcast transmission.
Same with the main sporting stadiums in NZ - Eden Park, Sky Stadium, all have fibre broadcast circuits. Run by Kordia
Other tracks have a satellite uplink set up, and its only an uplink, not a downlink. Just like this in the photo from Kumara.
Before fibre and the tab set up their own satellite linking trailers (in the photo) Kordia use to provide all the old analog links for the TAB.
Like in the Waikato, a tech from Kordia would come and point the dish to the top of Mount Te Aroha or Te Miro, or even the railyard at Frankton in Hamilton where Kordia had a mast and then the signal would be bounced up /or down their tv masts across the country.
As for the betting, that is totally separate from the tv broadcast side of the track connections. They have servers in those trailers you see parked up at the tracks and they obviously talk to servers back at TAB HQ and they also have a back up satellite system at each venue if the wired network was down or compromised.
they moved to IP based equipment a number of years ago for the wagering systems.