Apple probably knows that power users are buying non-Apple mice anyway so they can have multiple mouse buttons. Their mics have always been some degree of form over function (remember the puck mouse)?
But they get into this weirdness where they produce a well-designed functional product, people like it, they assume it's because of the design and then produce something else that sacrifices function for design, then act confounded when people don't like it.
I honestly don't understand Apple's apparent disdain for more than one mouse button though. The OS and apps support extra buttons, everyone knows how to right click by this point, what's the benefit? At one company where I worked everyone had a MacBook, apple monitor, apple keyboard, and a white Microsoft mouse.