Rulers measure cardinal quantities and not ordinal ones. There is no cardinal numbering scheme that starts at 1, all of them "start" at 0. For ordinal numbering schemes, the symbols are arbitrary anyway and you can start with whatever you want. It's equally valid to start with 1, 0, -1, A, or "aardvark". The only benefit to picking 1 as the start is to make it easier to count with your fingers while picking 0 lets you easily convert an ordinal quantity to a cardinal one.

Your job is to move apples from one bin to another. You pick up the first one and set it in the other bin, and say "zero."?

I've seen a lot of rulers that actually don't have a mark at 0 and instead go right to the edge as 0. Typically they are worn down, being made of wood, so the accuracy of the first inch is dubious. To ensure the distance is correct, sliding the ruler down one unit is a good idea. So, my ruler starts at 0 but my measurements start at 1.

Not on this side of the pond. We typically don't have a ground floor, that's just the first floor.

i wish the people making buildings around here knew that. some start at floor 3, others at 5. some start at 0. others at 2. every building has its own story. you need to understand the building before you can understand your position in it.