I kept my own surname when I married (ie, my father's surname). My DDs have their father's surname, and my surname as an additional middle name. Because our family already has a mix of surnames (mine and DH's) I can't imagine too many scenarios where I would actively change my kids' surnames. A complete breakdown of the father-child relationship, abuse, or crime, probably.

My mother changed her name when she married her 2nd husband, but then they divorced. 30 years later and she's still got her 2nd husband's name even though she hasn't seen him in decades, has nothing to do with any of his family or even a shared social circle. That's just downright WEIRD, if you ask me. If she'd changed our names at that time, we would have been faced with an additional layer of change and inconvenience when that marriage broke down. If she'd changed our names and then decided NOT to change them back, it would have been another layer of inconvenience to deal with in early adulthood, when you're setting up all the paperwork to do with tax, banking, study, finding somewhere to live, travel, etc.

In my mind, it's just easier and more elegant if everyone just keeps the name they were given when they were born!