Apple removed the scrollbar first, because they wanted the screen to look more beautiful and simpler. Instead you may not be able to tell that a page is scrollable, or maybe where you are on a page.

It's the definition of false simplicity.

Everyone followed suit because Apple Keynote events just made everything look so magical, and Mac/iPhone snobs were taken seriously by the dumbed-down press, and now Windows laptops and keyboards are like their previously-less-functional MacBook counterparts.