They don't know how to do it any other way. Don't think all the educators and administrators in this country wouldn't love to teach everybody all of those things. But the more people we want to succeed, the more it becomes obvious the broad swaths of our population that aren't prepared for it. So they cut back the "non-essentials". Then they cut out the "too-hards". Then when all else fails, they actually cheat on their own students' tests because they have failed to motivate those students to learn the pared down meaningless boredom that passes for school now. And I'm sure plenty of these educators have great ideas that could genuinely fix the system if only the idiots would get out of their way, but sadly idiocy is spread pretty evenly across all professions no matter how much we'd like for the better-paid administrators to actually be better at their own jobs.
That's our problem. It's not that any of these people fundamentally believe that it's impossible to properly educate all the unmotivated people. It's that they've tried and tried and failed almost every time and often just given up trying.