Sure devs have a choice.
"Crossing swords with Microsoft" is not really a choice for game developers. Not sane ones at least. Particularly since they have nothing to gain, and so much to lose from doing so. If they use DX9 Device it needs DX9 otherwise the devs could have used DX8 devices but would have had to sacrifice the high end hardware features of new shaders for example.
Yes. Obviously. However if they have no particular need for DX9 functionality, since 90% of their target audience does not have DirectX9 compliant hardware anyway, why would they want to make DX9 a requirement, if DX7 is sufficient? And on windows there is the choice of a simple click and 10MB download for DX9
Where? Microsoft report the size of DirectX9c going anywhere from 35-166 Megabytes. (Not to mention it takes considerably more clicks than that to find it). 20-50 clicks to find the opengl driver which is normally in the range of 20-50MB ...
First of all "Going to your graphics cards manufacturers website and clicking on the 'download drivers' button" is not 20-50 clicks and second of all, I have yet to see any drivers that are even close to 50 Megabytes, and even if they where it would be totally irrelevant because the exact same drivers are *also* needed for DirectX9 or you'll still not have access to "high end features of shaders".So let's go over the numbers:
Required for OpenGL: Recent graphics card drivers.
Required for DirectX9: The exact same recent graphics card drivers, plus an additional 35-167 megabyte download for an API abstraction layer.
No matter how you add up the above scores, OpenGL will always come out ahead, unless you have a recent WindowsXP SP2 installation, thus not needing to download DX9c, so you're breaking even.
So in the best case scenario you're breaking even, and in the worst case scenario (according to Microsoft) DirectX is an extra 167MB of downloads.
Beside that both are on any game related pc magazin :)
Yes. Thank you for pointing out the obvious. We've however already established that hardcore gamers do not generally encounter problems with having out-of-date drivers, and anyone else is not going to buy a game related PC magazine, particularly not to play some random game they just downloaded off the Internet.