I have this feeling that this is not a Finish thing, but a rest-of-the-world-apart-US, thing. In my ~40 years spent in Romania and now UK, I rarely saw people engaging strangers on public transport, let alone doing it loudly.
It felt bizarre.
Now if you're travelling towards another city in the UK chances are you won't get nearly as dramatic an effect.
Dense urban areas tends to have people withdrawing into a cocoon even many places where people are usually friendlier.
If we are in a pub, by all means, let's chat. I might even buy you the drinks for the rest of the night.
There is time for chatting and there is time for minding your <beep> mind. And I think I should get my British passport simply for believing and living by this idea.
Even where I live in South London, random strangers will say hi to you if you go for a walk in the park early enough in the morning, when they've not yet run into too many people. And then the later in the morning you go, the more people raises their shields.
My Belgian companion wisely kept his damn mouth shut the whole time.
It's not about likelyhood of talking, but how loud you speak. I feel like my inlaws (from the US) are constantly shouting.