Talk? To Whom?

This is a general, honest question about people.
I think that the answer might be in a form of self-protection for most, but I'm still puzzled.

So, before my friends start panicking, I'll state that I'm fine these days, but I still have questions about the way some people react to depression, depressed people and the shadow of suicide.

I'm puzzled because today, I met someone who'd left something in my postbox. He wasn't even surprised that I hadn't opened the box in a week when I said so.
He probably thought that I wasn't home, but in fact, I hadn't left my flat since the day before the one he put the note in my box. I was just working hard to plan my lessons, and since I had a full fridge, I didn't leave my nest.
I could have been unwell or depressed, but he didn't say a thing.
Are we just all being too polite?
"Are you fine?"
"Yes, thank you. And you?"
"Fine, thank you."
Are we drowning in formulas?
Do we care?
This is one thing that disturbed me.

Then, twice in the past, I asked contacts to check on me if I ever became silent on the net.
No one cared.
I could be slime on my floor by now. No one cared to check on me when I did disappear because, yes, back then, I was depressed and needed someone, anyone to wave my way.
That was the Internet, where people care and don't care... Okay.

I've seen people encourage depressed people to speak and contact friends, relatives or complete strangers if they think about death.
Fine.
All right.
Short of phoning the Samaritans, to whom can you turn when you've no contact with your relatives (who wouldn't care anyway), when the people around you are being polite (but not interested in your life), and icing on the cake, when your friends to whom you mention suicide ignore what you just said?
Back when I was feeling down because I'd just lost two people to suicide, I felt extremely low. I did try to speak, and no one listened.
What do you do then?