Yes but the thing you see as shield walls and pikes and such are not some grand teamwork plans, that is just people adapting to the map that is presented to them. Just like in city maps you have archers going on roofs, or shielders atacking archers, groups advancing on each other etc, village map camping hills or villages and such.
My point being: just because it doesent look like some kind of formation doesent mean that teamwork isnt being used. Teamwork is a integral part of every map not just plains. It is just more obvious at plains maps because you can see all the people together in clusters (mainly in this way protecting themselves from being picked off) and other would be formations that the map requires.
You're still missing the point. People jumping on roofs ect is all very well, but it's still just them working by themselves. I know there are small pockets of team work, but I rarely see a group of infantry actually working together (other than following each other towards the enemy), or cavalry forming together or archers focusing attacks. I'm talking about one or 2 guys taking command (hell we have a command system for a reason, otherwise just take it out of crpg) and some taking charge of cavalry, as a group, some of infantry, as a group, and some of archers ect, as a group. You never see that. It wasn't adaptation, it just happened that there were a few guys handing out orders and once you get a small group together, people tend to flock to that until they realise teamwork is actually helpful.
Again, I'm just saying, there aren't many pure open plains maps. They are either camp village, camp hill or random brawls. Cav formations aren't seen because often there's no point when everyone is on their own. When GK are together, regardless of the map, we form up together. Only the town maps we don't because you can't do it in a street very easily. But infantry ect don't work together on a big scale (which would be very useful on street maps) and the majority of the time archers don't all help each other out, focus fire on certain players/horses ect. But the point being, most maps you don't really need to work together because your in amongst the enemy and essentially reliant on your own skill.
Open plains maps require that you work together else you'll be caught out on your own in the wide open. Honestly I think they are more realistic. How many sieges ect actually ended up with open fighting in the streets between armies or two large bodies of men fighting over one tiny village? I just feel like they are a bit more realistic and so add a form of excitement to the game. I did say I don't expect every map to be this way. But it would be nice to see a few more of them.
EDIT: Sorry if my editing is a bit sporadic. I tend to post then edit and add stuff as I think of it later.