It is actually more useful for 1 to not be considered prime in terms of application of the concept, as the other comments mentioned. Of course it’s artificial, all of math is. But the artificial definitions in science only stay in place if they’re actually useful.
Prime is just a artifical restriction, like, a blue sky is only a sky if it’s blue.
1 / 2 is 0.5, a half. Nothing special about it.
It is actually more useful for 1 to not be considered prime in terms of application of the concept, as the other comments mentioned. Of course it’s artificial, all of math is. But the artificial definitions in science only stay in place if they’re actually useful.