re: rookie razzing.... an important documented sociological function of razzing (mildly picking on your noobs to make them feel mildly bad, somewhat annoyed) is as a "testing" ground for loyalty and response (will you observe our authority? if so, we will permit you to be one of us. if you don't observe our authority but in the correct way, we will also let you be one of us. haha). i think it's also just a way to Provide Attention + Belonging without making it obviously a form of "Care", which, especially in male/masculine environments, signals an insult of some kind (you need caring for).
but i think a further underobserved utility is that it gives someone new a specific thing to feel weird about. if you're new you're going to feel weird no matter what but now it has directionality and cause, and when people stop being kind of mean to you, you can stop feeling weird. simples. as opposed to everyone being nice to you from the start and therefore the problem of the weirdness is you. them being a bit of a dick allows the problem to be external. and that can be helpful.