Principal is the fact that there is a lot you can't make OS X do, not necessarily because Apple have decided it's a bad idea, but because they can't easily conceive of why anyone would want to do that.
This is a very extreme example, but I found a blog post a few years ago about some enterprising soul trying to create focus-follows-mouse in OS X. The TL;DR is: there is a basic assumption to the design of keyboard shortcuts that require the menu to be correct and it is this that prevents focus-follows-mouse from being implementable. And behind that is that Apple OS devs cannot understand what focus-follow-mouse is.
Wade.
This is a very extreme example, but I found a blog post a few years ago about some enterprising soul trying to create focus-follows-mouse in OS X. The TL;DR is: there is a basic assumption to the design of keyboard shortcuts that require the menu to be correct and it is this that prevents focus-follows-mouse from being implementable. And behind that is that Apple OS devs cannot understand what focus-follow-mouse is.
Wade.