Related: Why can't variable names start with numbers?
Is there a technical reason why spaces aren't allowed in variable names or is it down to convention?
For example, what's stopping us from doing something like this?:
average score = sum of scores / number of scores
The only issue that comes to mind is keywords, but one could simply restrict the use of them in a variable name, and the lexer would be able to distinguish between part of a variable and a keyword.