why OSX cannot write depth per fragment?

in the depth buffer documentation i see this:

• On OpenGL (Mac OS X), depth texture is the native OpenGL depth buffer (see ARB_depth_texture).
  • Graphics card must support OpenGL 1.4 or ARB_depth_texture extension.
  • Depth texture corresponds to Z buffer contents that are rendered, it does not use the result from the fragment program.

why is this a limitation? its insanely frustrating!

gl_fragDepth is supported in ALL versions of OpenGL!

https://www.opengl.org/sdk/docs/man/html/gl_FragDepth.xhtml

can anyone explain why they would take this incredibly useful feature away?

 

I suggest trying it anyway, just to see if it works. I have heard several backwards things about macs, and some of them have taught me; try anyway, they often say one thing when it is the other way round!