I hate to trot out the tired old "because toys" argument, but because, well, toys. They are still selling GT stuff, in general. Dokkan battle has two GT events, and GT sets of cards. They still sell GT gasha. There were two upcoming SSJ4 figures posted in this very thread. And obviously it's worth mentioning all the GT content in Heroes, which makes truckloads of money (apparently). In addition to all of that stuff, the mere existence of Super/Kai raises the awareness of DB everything to new and returning fans who are likely to seek out GT, which means that it could be still sold as a fresh product. Speaking personally, I did not watch GT until I started watching Super. Herms will be doing commentary on GT after Z and I'd bet that there will be people who will check it out for the first time when he does that. It is still a moving product and I do believe that Toei will go out of their way to prevent that part of the DB brand from being damaged.
I agree that Toriyama probably doesn't care about GT. I'm not sure if Dragon Ball Minus is a great example. While it does obviously not play nice with the Bardock special, there isn't an anime adaptation of it, so people watching the anime only (which makes up a sizable portion of the DB fanbase) would never know it existed, so it doesn't exactly compete with the Special.
Again, I am doubtful that they will link Super to GT, let alone acknowledge it. Will Super conclude with EoZ, shortly after which being where GT picks up? And, I do think that there are obviously plenty of reasonable arguments as to why Super contradicts GT/they aren't in the same continuity, but I think there are just as reasonable arguments as to why it doesn't necessarily or explicitly contradict GT. I just personally don't think it's as clear as people make it out to be.
fwiw if they do manage to tie it in with EoZ and or GT I don't think it'll be Zeno pressing the "reset button" or whatever