Umm, then you clearly have no idea what UDP is for...
UDP is the standard protocol for any online action game, it's slim headers enable a very small overhead, which is very VERY important when dealing with the internet, which is incredibly slow compared to a LAN. As opposed to TCP, which is good for slower data, it automatically corrects errors, you don't need to worry about if it reaches the other end or what order it gets there in, because all that is sorted for you. Of course the headers are larger and almost prohibitive for an action game with a lot of stuff that needs updating.
UDP is the standard protocol for any online action game, it's slim headers enable a very small overhead, which is very VERY important when dealing with the internet, which is incredibly slow compared to a LAN. As opposed to TCP, which is good for slower data, it automatically corrects errors, you don't need to worry about if it reaches the other end or what order it gets there in, because all that is sorted for you. Of course the headers are larger and almost prohibitive for an action game with a lot of stuff that needs updating.