Big endian
The convention where the leftmost Qubit is the zeroth qubit is called big endian. 1
It is used to convert qubits from their binary string representation to the decimal representation, i.e. ${\ket{000}, \ket{100}, \ket{010} …, \ket{111}} \rightarrow \ket 0, \ket 1, \ket 2, …, \ket 7$.
In this convention, we label qubits left-to-right, starting with zero. e.g. the decimal representation of a qubit $\ket {b_2, b_1, b_0}$ would be $2^0b_2 + 2^1b_1 + 2^2b_0$.
Its inverse is known as the Little endian.
# Uses
This convention is most famously used in Quantum Computation and Quantum Information.