A few military bullets have been designed to yaw, but for the most part it is not desirable. It is a bit silly to think that an enemy soldier shot with a full power rifle won't be bothered unless the bullet yaws or has a hollow point.
Further, an unstable bullet might produce a more severe wound in a human body, but it will not penetrate cover as well, a drawback in combat.
The military often has other concerns, not always obvious. The Army adopted a flat base 150 grain bullet with the .30-'06 cartridge. But in WWI, it was outranged by the German 8mm. So the U.S. went to a boat-tail bullet that had a longer range. Then they found out that the range was so great that bullets were striking outside the impact area of military ranges, not a good thing to have happen. So, back to the flat base bullet, which served as long as the .30 remained in service.