The point of requiring signatures was never about preventing fraud, since it was never an issue historically. The requirements were issued in the 20th century to reject black votes, as at the time the requirements were passed, many black voters couldn't write.
States like Oregon and Colorado imposed signature requirements in mail in voting systems designed in the last few decades. Switzerland requires signatures for mail in votes too.
https://www.theatlantic.com/ideas/archive/2020/10/signature-...
The point of requiring signatures was never about preventing fraud, since it was never an issue historically. The requirements were issued in the 20th century to reject black votes, as at the time the requirements were passed, many black voters couldn't write.