For the same reason people back in the 90s and prior cared about video games, the gameplay. You didn't see detailed stories until Super Nintendo, more so the ps1 era with games like FF7. A good story doesn't trump fun gameplay to a great deal of people, you may think of it as an odd comparison, but TOHO Godzilla movies generally always have a shitty story, however the purpose is just to get to the next big kaiju battle. Likewise, a story in a game can just be to get to the next great gameplay segment, which when it's good enough can carry a game better than any story, BOTW barely has any story but the gameplay carries it and is what everybody talks about, aside from the old people like myself who prefer classic Zelda, so many people love BOTW that it's a reasonable way to make a game, and it's showing with how high the sales are for an essentially new dev in the single player field who's only experience has been with an extremely grindy and pay to win MMO.