As a beginner Mandarin learner, my understanding is that historically, people wrote using the traditional stroke order, this informed what people think of as the aesthetically pleasing or "correct" way that the characters look. Now, if you want to write the characters in a legible and aesthetically pleasing way, the easiest method is to write them in the traditional stroke order. I think it's analogous to the way cursive writing in the west was taught, which informed the way it was written and what people thought of as the "correct" way to write cursive. If you wanted to learn to write in cursive, you could just look at existing cursive writing and try to copy it, but if for example you guessed that you should write it from right to left then you'd probably find it harder because cursive evolved to be written from left to right.
You can normally tell when someone uses the incorrect stroke order because things will be the wrong size. For example, when writing 因 you're supposed to write the outer ㄇ first, then the inner 大 and then the bottom horizontal stroke of the 口. If you start with the 大 then it's harder to write the outer 口 the right size.
Again, this is all from a beginner, so take it with a good amount of salt.
You can normally tell when someone uses the incorrect stroke order because things will be the wrong size. For example, when writing 因 you're supposed to write the outer ㄇ first, then the inner 大 and then the bottom horizontal stroke of the 口. If you start with the 大 then it's harder to write the outer 口 the right size.
Again, this is all from a beginner, so take it with a good amount of salt.