On other layouts that isn't enough. For example French keyboards are AZERTY, not QWERTY. and here in Sweden we have å, ä and ö next to the (tall) enter key, instead of the symbols US and UK have.

(Side note: those are not a and o with diacretics, they are entirely separate letters in the alphabets of the Nordic countries, with entirely different sounds.)

Not all password policies allow you to ignore special characters.