Why don't underscores in numbers enforce proper formatting?

[ixid]

The underscores in values such as 1_000_000 aid readability but 
DMD doesn't see anything wrong with any placement of underscores 
as long as they follow a number. Is there any reason to allow 
uses like 1_00_000, which are typos or exceedingly lazy 
modifications of value, and not enforce digits to form sets of 
three after the first underscore?