First floor vs ground floor, usage origin

You can read this article and make your own assumption about why Americans use such a system: https://en.wikipedia.org/wiki/Storey#Numbering

In my opinion, when you use the word "floor", you should start from 1 (on the ground). Because you have a floor (surface) there, don't you? This is logical.

The American convention is that the floor inside a building which is on the ground, is called the first floor and the floor above that is called the second floor and so forth.

Why the difference?

This is my theory: The term ground doesn't need to be qualified, there is no such thing as a ‘second ground’ whereas any building can have one or more floors or storeys. Neverless in many hotels, the first floor is often referred to as a lobby

First Floor/ Ground Floor
In the US, the first floor of a building is also the ground floor, but in Europe the first floor is the floor above the ground floor, and the second floor is the one above that. This is important information for novice American travelers trying to find their hotel rooms.
_{Paul Brians’ Common Errors in English Usage}

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_{Images from English Club.com}

An American native speaker on Word Reference writes

We use "ground floor" and "first floor" interchangeably. If you walk up a flight of stairs, you reach the second floor, whether you call the floor you started on the ground floor or the first.

Similarly on a different English language forum, a native speaker confirms

In the US, “ground floor” and “first floor” mean the same thing and are used interchangeably. Usually elevator buttons marked ‘B1’, ‘B2’ etc. do indeed refer to “basement”. Sometimes they will say ‘LL1’, ‘LL2’, which stands for “lower level” (but still means “basement”.)