3.2GB texture limit

Hello,

I am writing application for viewing images and encountered one limit in 
texture size that I am not sure why is there.

My GPU Radeon 6700XT have maximum texture size 16384. I can allocate 2D 
texture 16384x16384 for GL_RGBA, GL_RGBA16 but GL_RGBA32F. This will 
result in GL_OUT_OF_MEMORY. Maxmimum size for GL_RGBA32F is 14191.

That is 3.2GB of VRAM so with 12GB of VRAM there should be plenty room 
so not sure why it fail.

I am mostly curious why limit is this size and not other. BTW software 
rendering LIBGL_ALWAYS_SOFTWARE=1 have this limit even lower.

Regards.