Not enough people give a shit about "general purpose computing" to matter. They use computers for a few things and as long as they can do those things they're fine with it. My wife loves all her Apple gear. It provides her with a wonderful, curated experience. Okay, maybe it hasn't been so good with recent iOS releases but it still beats Android or Microslop. Being able to hack, modify, or install arbitrary stuff on your device is something only a minority of a minority care about, statistical noise in the quarterly sales figures. When you compare that to the harm done by malware, illegal or indecent material, and the negative blowback to YOUR OS's reputation—or worse, the "felony contempt of business model" enabled by a general-purpose OS (piracy, ad blocking, etc.)—it's a no-brainer to implement restrictions.