I don't know what servers you have spectated. It could of course just be linked to the time of day you observed and your location. If you join a North American server around 3pm est (or anytime during normal working hours), you can pretty well expect to find that school age kids make up the vast majority of players. (I'm generalizing, I know, and enough had been said about the average maturity level of the American <20 year old.) Play in the evenings 10pm -1am est and these guys are pretty well tucked into bed and their parents or older siblings are playing.
Many of the European servers that I have been on offer teamwork, but if you don't speak the language it can be problem. Not that they won't reply to you in English, but you have to respect the fact that they will be conversing amongst themselves in their native tongue. If you don't speak the language, you may miss out on some of the strategy. Sadly, one of the problems with keeping NA servers full is that very few Americans speak any language other than their own.
There are several NA servers that some of the "elderly" frequent with regularity. There is almost always teamwork involved and mature noobs that ask intelligent questions are welcomed and coddled with open arms.
Having said the above, and in concert with what zetsumei says, most RO players have a little more respect for each other than might be found in other games. On a lot of servers, a message of "I pwned u" is generally met with a onslaught of disdain and the person saying it ends up getting "pwnd" and leaving from the sheer embarassment of having opened their squeaky little mouth.
In answer to your question...
I can't speak for the daylight hours, but in the evenings, the =OF= Old Farts server and the ro50pc server always seem to have a lot of teamwork going on.
Floyd