Oh, no! -- you can't make money without substantial market share! Better sell my Apple stock! <pulls out remaining hair>
Its a valid point. In the case of the Mac Apple is making a MAJOR killing off their hardware. Substantially better then the cutthroat prices that PC manufacturers are selling their wares at.
The two reasons I never expect Apple to EVER release OS X for the generic PC is two fold. First is drivers and support. Both of these things are expensive overheads to the OS. Apple as it stands has to support a very small, very specific set of hardware parameters. Granted its grown since the release of OS X on Intel but compared to the PC industry in its entirety its a drop in the ocean. The minute Apple releases OS X for PC generica they run into the same problems that MS runs into. Namely driver hell. Apple doesn't want to get into that. Nor do they want to hand the responsibility of the stability of OS X over to companies like Dell. Because drivers can and frequently do make or break a systems stability.
The second reason is also pretty obvious. Apple makes most of their money on the hardware. The minute they release OS X into the wild for the generic PC they will no doubt start raking in money hand over fist. The problem isn't now. The problem is in 2, 5, 10 years where OS X has saturated the market just like Windows has. In Microsoft's case they are having a DANG hard time convincing people to upgrade because for many, like myself, XP/2K is a perfectly fine OS. Once Apple has saturated the market sales will start to slow. Its better for Apple to be in the position that they are and have nowhere to go but up instead of hitting a concrete ceiling. People need to realize that PC users arent Mac users. They would buy Tiger and then sit on it until the system dies. At which time they would upgrade their hardware and their OS. Apples formula is perfectly fine.