The "pushy" or "forward" nature is not something that afflicts the "christian" types alone. That might be the one you notice most or bugs you, which I do understand.
It annoys me too.
There are many who immediately begin chatting up their intrests whether or not one is even slightly interested or not. One of my relatives does this with the weather. I am thinking, geeze shut up already, I can see its partly cloudy.

Another aspect of this behaviour among Bible thumpers is I think brought about by the misconceptions concerning being a 'witness'. Like the dude that stands in front the Braves game or rock concert and screams Biblical teachings mixed with nonsense.
Some have the notion that this is what the Bible is refering to when it makes reference to being a witness for Christ/truth etc. Unfortunately theyve missed the boat on that one. The witness is SUPPOSED to be HOW you treat people, NOT preaching at them or dragging them into your religion.

Some are just showing genuine concern although perhaps not in the best way.

Then too some people are just oblivious.