There are good reasons why we follow strict and logical rules in maths. Evaluating expressions involving numbers is one of the basic tasks in arithmetic. But if an expression is complicated then it may not be clear which part of it should be evaluated first, and so some rules must be established.
Things like the “order of operations” may be phrased in simplistic terms such as BIMDAS or PEDMAS etc. to aid memory recall, but the user still needs to know how to implement the rules properly and to be aware of any underlying assumptions. Otherwise they can end up making incorrect assumptions and getting the incorrect answer.
We also need consistency and accuracy in definitions and a common language so that we can follow correct logic and and so that we can discuss problems with others.
Of course this does not just apply to maths, but to many aspects of life in general.