Why there is no ALPHA component in COLOR buffer?

OpenGL OpenGL: Advanced Coding
1

subj. in W98
MSDN says - Alpha bitplanes are not supported.
Is this right?

2

MSDN claims are generally only valid for the generic, software, Microsoft implementation of OpenGL.

Alpha bitplanes are supported in hardware for quite all video cards nowadays, assuming you’re in 32 bits colors.

Y.