Where I'm from, we merge at the last second and if possible, create a double merge if traffic gets bad because we're stupid and in a rush all the time. I'm from New York if you can't tell. Personally I do whatever looks most convenient (usually zipper).
I've lived in Illinois, Connecticut, and California, and it's definitely a regional thing. I've heard that in Wisconsin they call us FIAs (fucking Illinois Assholes). Not to the point but funny nonetheless.
When in Connecticut (being a car clown, as I still am) I drove in NYC quite a bit. And for all the mass hysteria (mostly from those not from there) about the terrible traffic and whatnot, I found driving in the city to be the best experience ever. So many people in such a tight space leads to a communal push for everyone to get where they are going - zipper merges, scooting close to the car in front of you (because everyone has been the guy at the end of the line accidentally stuck in the previous intersection), taking off and getting up to speed quickly when the light turns green. Required a lot of attention, but I thought it was really fun!
In Illinois, in town, there are a couple of intersections where pre-light it's two lanes and shortly after the light it goes down to one. I always line up in the lane that will continue. Because it's not construction and we all know what's about to go down. Then 2-3 people line up in the lane that will end and I'm always hoping for us to hold the line and not let them in, because as in elementary school "I was here first!"
I like to think of people in grocery stores with carts - we are so nice to each other when it's crowded, letting people merge into an aisle, etc, but given the same scenario in a car and we are enraged! Protective car bubbles can make us forget our humanity.