Why ​摺 in Simplified Texts and not 折?
折 is not a simplified character. 摺 just happens to be a rarer character that means the same thing, namely to fold (v), or folder (n).

折 is here much more versatile, and has additional connotations, such as break, lose, die, act, and so on.

Here we have words such as 打摺 (fold), which is obviously not the same as 打折 (make a discount).