They want this as long as they are not the dominant platform. If MS and Apple swapped places tonight and Apple suddenly had 90%+ marketshare, it's likely that their strategies would flip just as fast, because it's the most profitable thing to do.
Apple's interests are in ensuring that their platforms can run as much user-desired content as possible; they can do this by promoting cross-platform compatibility and interpreted code like JS and HTML.
Microsoft has no need for this, since everything runs on Microsoft by default, because if it didn't, you'd miss out on 90%+ of your potential market. Instead, Microsoft's interests are opposite; they want to do everything they can to ensure that Windows is still required for any and all meaningful usage. This is the major point of IE; do enough to mostly work, but break compatibility where you can get away with it so that developers can't forget about Windows and IE.
They also hope, though the environment isn't appropriate for this to work anymore, that IE will be your sole development platform and that considering the time it takes to make stuff work in IE, you will just leave things broken in all other browsers, further solidifying the MS lock-in.
Lock-in is the holy grail for the software vendor. Apple is putting this in place as best as they can in the markets they control, and they are trying to ensure that MS doesn't lock them out of the desktop game, because they're still vulnerable believe it or not. MS is trying to ensure that Windows' death grip remains in place FOR. EVER., just as Apple wants iPhone/iPod to do the same.
They are a software vendor, and by vendor I mean producer. They don't not become a software vendor because they bundle the software and hardware together. They may make money on their hardware which is great for them, but it doesn't change the fact that OS X, iTunes, and the others, like all other software platforms, want lock-in; Apple merely wants to lock you in to the hardware too, so they use the software platforms to do that.
They want this as long as they are not the dominant platform. If MS and Apple swapped places tonight and Apple suddenly had 90%+ marketshare, it's likely that their strategies would flip just as fast, because it's the most profitable thing to do.
Apple's interests are in ensuring that their platforms can run as much user-desired content as possible; they can do this by promoting cross-platform compatibility and interpreted code like JS and HTML.
Microsoft has no need for this, since everything runs on Microsoft by default, because if it didn't, you'd miss out on 90%+ of your potential market. Instead, Microsoft's interests are opposite; they want to do everything they can to ensure that Windows is still required for any and all meaningful usage. This is the major point of IE; do enough to mostly work, but break compatibility where you can get away with it so that developers can't forget about Windows and IE.
They also hope, though the environment isn't appropriate for this to work anymore, that IE will be your sole development platform and that considering the time it takes to make stuff work in IE, you will just leave things broken in all other browsers, further solidifying the MS lock-in.
Lock-in is the holy grail for the software vendor. Apple is putting this in place as best as they can in the markets they control, and they are trying to ensure that MS doesn't lock them out of the desktop game, because they're still vulnerable believe it or not. MS is trying to ensure that Windows' death grip remains in place FOR. EVER., just as Apple wants iPhone/iPod to do the same.