Sandi

Did you read ALL my post

"Because I don't nod where it would be inappropriate, where it would be inconvenient or dangerous to return it

"
I've been riding almost 50 years

Don't you think that by now I've worked out where it's safe to nod

As for "why" return a nod

Because it's "common courtesy" that's why

It's like saying good morning to someone or good evening

And them totally ignoring you

Would you like it if you said "good morning" to your nieghbour and they just "blanked" you
It is just good manners