It's a survival thing, I guess. We're always ready for war even if we're not always ready to instigate it. Our imperial anthem is literally titled 'Die for the Cause,' though.
Only other species we can technically breed with are the asari, but it's not like the offspring come out looking like a mix of the parents. They'll be born asari despite the differences. Human-turian relations are a little tense because of an old war but it's supposed to be easing up. My turian father would raise his non-existent eyebrow at, say, me marrying Cindy, but he'd come to accept it with time.