Why you can not use numbers at the beginning of a variable name in many programming languages?

In many programming languages, variable names must start with a letter or an underscore because using numbers at the beginning can create ambiguity in parsing the code. If a variable name began with a number, it could be misinterpreted as a numeric literal rather than a variable identifier. This rule helps maintain clarity and consistency in the syntax of the language, allowing the compiler or interpreter to correctly understand the intended operations.