[Xorakios]

Some special characters are not processed as one might expect, particularly by implementations of languages such as COBOL, which is still used on the server side by many banks, insurance companies and government agencies where consistency is paramount.

"#" can mean phone number "+" or "&" can mean concatenate variables

It is vastly easier to screen out possible problems at the user/browser level than rewrite zillions of lines of legacy code.