The order of operations helps keep answers for multi-step equations similar. If the proper order of operations are not followed, then answers may vary. To show an example:
4 / 2 - 1
The proper order of operations would be:
Divide first, before subtracting
4 / 2 - 1
2 - 1
1
But if subtracting was done before dividing:
4 / 2 - 1
4 / 1
4
So not following the proper order would yield different and erroneous answers.