Because they’re NORMAL. Only the fanatics force Linux into every conversation possible. The normal ones just read the insane comments and roll their eyes. They know better than to get into an online argument with the obsessed.
Whenever someone tells me about the problem they're having on Windows (which I haven't used on my computer in years) or any Apple OS I explain how I would fix it Linux if I don't happen to know how on their OS. If the Linux way is easier I also usually give it as a comparison.
I only really do this with people who I know could easily get Linux working and people already interested in Linux.