Last name questions?

I understand the confusion with deciding what last name to give your child but I don't understand why people bring up marriage as a reason to not know which name to give your child. Do you guys know that even when you do get married later on that doesn't automatically change your child's name too. So even if you wanted to switch your child's name to your name, your married name, or remove the birth father name, you still have to go through a process to do it and even sometimes pay. So please stop using married as a reason not to because out of all the actual reason on why not to or to do it that's not a real reason. Sorry for the rant but I've read so many post that's stated it. I could be wrong and it could differ in different states, but where I'm from being or getting married doesn't make that any more or less complicated.