I think 90% of the time arguing with someone will not change someone's opinion on something since most arguments don't have very good evidence. Plus, a lot of people think they are right, and others opinions who are different are wrong.
A lot of the time, people just pretend to agree, so they can go on with their lives since many people have better things to do then argue about something like Judge Judy will kick Judge Joe Brown in an arm wrestling match...epic
Sometimes people just agree to avoid being beaten up by the class bully, or outcast by society for believing in something labeled Immoral by many people like having multiple wives or girl friends.
Yeah i know a lot of people always think their right and will not agree with anyone and fight to the death about some stupid topics, but yeah their are also people who just agree and go one with their daily lives. Usually i wont even bother to argue only if its about something a now a lot about and can back it up. Usually bullies never tried to deal with me so i wouldn't know much about that area. But being into the social outcast area, well i know some stuff about that, hell i was put into the geek/nerd catagory along time ago, but still had friends from all over, even if your in a catagory, you still may do something way different in your life thats apart from what people think of you.
Debating is not arguing. The point of a debate is to education people on either side of an issue and then discuss it from there. When people get really heated and start arguing, they are really losing focus of the debate. (That's why it's hard to debate hot topics like abortion and the death penalty.)
I am pretty sure that for some it can, and does, but for others, it just helps them see the other side's P.O.V. Personally, I don't care to convince someone.. or whether or not they agree with it. They'll either understand where I am coming from, or they won't. Either way, it doesn't concern me and I won't be losing any sleep over whether or not they do agree. Personally, I usually just leave my opinion on the topic, and move on.. and if necessary, and in rare occurrences, defend it.