The first scientist says ‘I’ll have a glass of H2O”
The second scientist says ‘I’ll have a glass of water too. Wh… why did you say H2O? Like, I know it’s the chemical formula for water and all, but it’s the end of the day and there’s really no need to intentionally over-complicate things like that in a situation outside of work”
The first scientist stares at his drink, angry that his assassination plan has failed.
Voldemort rose to power in 1997. He destroyed all records of muggle borns. Therefore, all muggle borns that would have been younger than 11 at the time of his takeover would never have gotten their letters because he's an evil wizard and destroyed our records. The Ministry is still in the process of finding all muggle borns.