Except that for checks, it's not the numerical part written in the little box that matters, it's the full written amount e.g. 'Five Thousand Three Hundred Fourty-Seven and 33/100' for 5,347.33.
Similar rationale, though, because it's easier to modify a number (say, change a 7 to a 9) than to change a full word.
Similar rationale, though, because it's easier to modify a number (say, change a 7 to a 9) than to change a full word.