It boils down to a couple of things.... safety, and convenience.

The Spitfire is cthe classic example. All Mk's of the spit prior to the XIV, I believe, used the Griffon engine, which was "left hand rule" turning. This induced a yaw to the right on take-off. The MkXIV included the Merlin engine which was "right-hand rule". The only practical difference between the very popular MkV and IX was the change in engine. There were a number of incidents where people almost crashed on take-off because the Yaw was now to the left and the pilots were not expecting it. Ground-loops happened, etc. So, they standardised on one engine rotation direction to make it easier to anticipate the characteristics of a plane. The Americans mostly had "right-hand-rule" engines, and left hand engines were no longer developed.

The other reason is design simplicity. People have natural right-handed or left-handedness, and people engineering engines would have a natural "bent" to think of an engine in a particular way. Just like the production lines are set up to have the engines oriented a certain way. Basically, it is easier to just have to manage one basic engine concept than to have to manage two.

So, there is no scientific reason other than plain convenience.

gus